This happened a few weeks ago. I'm playing a Phenax, God of Deception deck with Phenax in play and cast Tree of Perdition. Somehow the tree survives a trip around the table. I pass with the it untapped.

The player to my left is playing Atraxa and has Ajani Steadfast in play with five counters. He has one other creature that's been forced to attack a Gideon, Battle-forged this turn, and plays a Deepglow Skate doubling Ajani's counters.

He ultimates Ajani to gain near-total damage prevention; in response I use the Tree of Perdition to keep his life at a manageable 13 as well as pump my Tree's toughness to the moon.

The player to the left of my Ajani opponent, however, has a response - he casts Ovinize on the tree, bringing the Ajani player's life to 1 instead of 13.

The Ovinize guy then takes him out of the game next turn with a single attacker, since the Deepglow Skate came in tapped due to a Thalia, Heretic Cathar elsewhere on the battelfield.

Paradoxical Outcome is one of my favorite new cards...

Playing my Ephara deck earlier tonight in a four player planechase EDH game. We're on the plane that copies every instant and sorcery cast. Saskia player casts a Reclamation Sage and targets my Leyline of Anticipation to destroy it. In response, I cast the outcome. The copy bounces Sol Ring, Top, Mox Opal and an Aether Vial with no counters on it. Draw 4 cards then flash it all in again to bounce again with the original copy as well as the leyline for another 4 (leaving the Vial in play). Next turn recast everything and didn't even need to discard...

Few turns later I get to snapcaster it back for even more ridiculous draw while saving my board.

I don't mean to rain on your parade but this doesn't work. When you cast the original spell you had to select targets as it was put on the stack. Let's for arguments sake call them A, B, C, D and E. When the ability of Izzet Steam Maze copies the spell, and you target A, B, C & D then return them to your hand, even if you flash them back into play, they are new objects F, G, H and I, so the original can only continue targeting E. If you targeted the same 4 permanents with both, then the second one would be countered on resolution for having no legal targets

Doh. For some reason I didn't think it targeted. Still would have been pretty epic just drew a few extra cards than I should and had to waste time recasting stuff that I didn't need to the following turn.

There's an obnoxious deck 'round here that abuses Deadeye Navigator in lots of ways, and protects it quite well. He was doing his shit last Saturday again, untill the new player at the table asked me "Hey, my Containment Priest that's been lying here since turn two, doesn't that interact with this bouncing and returning?" ... None of us ever noticed, CP is played frequently, but somehow every long time player completely missed the fact that it shuts down DEN completely, and the newbie had to remind us to RTFC

Playing an extremely casual 4-way: Gonti (me), Vish Kal, Xenagos & Ashling (the Extinguisher).

Xenagos did nothing all game so it was essentially a 3 man & a punchbag. Ashling is slowly building up her board until she has pretty much everything she needs to win including a Geth chipping away at my yard.

I manage to kill the Geth and reanimate it though I have Dark Mike in play so if the Geth dies it goes right back to Ashling with Mikaeus's Undying-granting ability. The only issue is that she has next to nothing in her graveyard for Geth to reanimate, no big juicy 6cc monsters that would start the ball rolling.

I grab a Lightning Greaves which mills a land and a Phage (don't want that!) and all that's left are two 1/1s for B that net me spells that I can't get either. She just keeps dropping monsters, stealing things from graveyards and chipping away slowly at everyone. I need to find a way to clear the table without giving Geth back to her and all I have is a Black Zenith, which is useless.

And Vish Kal is starting to build up his board too, so between various swampwalkers and fliers, I'm getting squeezed.

Then Xenagos, after his usual Land-go turn, says to Ashling "What you need is a Sheoldred to get through on swampwalk and break up their boards. You'll eventually get Geth back and you'll be able to plunder their 'yards." To which Ashling replies:

"Actually, funny you should say that...!" and drops Sheoldred, she attacks, passes the turn and looks up to see 3 faces smiling back at her.

"What?"

"Oh nothing, nothing!"

I untap, Gonti flickers through my yard thanks to Sheoldred/Mikaeus and I target Vish Kal before quickly passing the turn.

Vish Kal loses a vampire, replaces it and passes the turn. Everyone is cracking up because Ashling hasn't seen it yet.

Xenagos plays a land and says "Everybody ready? GO!"

Ashling is truely perplexed and starting to get a little peeved, untaps and goes to draw a card. "Don't forget the Sheoldred trigger."

She smiles and goes to her graveyard and her hand is halfway there when she realises she's probably toast. Sure enough, the only creature or artifact remaining in her graveyard was Phage the Untouchable and she dies to her own trigger with much amusement.

Did she switch the card out of the deck, after that? (that would be a pity, personally I love this kind of "high-risk, high-reward" cards)

Nope, it's been there for a while and we've generally managed to kill it or die to it or exile it before situations like this arose. This happening is probably half the reason she plays it, to be honest.

Had a game a few weeks back with myself playing Kambal vs Brago and a Sultai zombie deck.

Brago had started getting out of hand and was flickering everything for value and countering everything we had tried to play that might threaten him. I made an attempt to remove Brago when he swung at me only to take another counterspell. He blinks his board with a Panharmonicon out to make things even worse for us... One of his blink targets happens to be Jace's Mindseeker, first trigger hits nothing. Second trigger hits Beacon of Immortality which he gladly cast as I'd been draining him pretty badly all game from Kambal triggers. At which point I respond with False Cure and ask if he's got another counterspell in hand. He tried to dig for one with things he had in play but luckily couldn't find one and couldn't believe that he lost the game from such a commanding position.

The turn goes to the zombie player who happens to have a doubling season and a few zombies in play vs my completely empty board, he creates a ton more zombie tokens, hits me with what he could down to ~50 ish life (Kambal's life gain adds up) and passes the turn. Yet another perfect spell off the top as I draw and cast a Blinding Angel. Zombies hits me for a ton taking me down to ~10 only to have me stabilize with the Blinding Angel. A few turns goes by and neither of us draw a board wipe/spot removal or alternate win con. I then pull a pair of boots and give the angel hexproof and he concedes defeat since he can't deal with my angel.

First time I hit Doubling Season into Tamiyo, Field Researcher today. Yikes!

My opponent was playing one-shot Werewolves and sculpting a play to drop Ulrich into Xenagos with Ascetism on the board and decided not to kill the Doubling Season right away. I mean, what's the worst that could happen, right?

I finished my turn with a million Jaces, 2 million illusionary drakes, 60 vampires, and Ajani primed to give everyone +10 loyalty & 10 +1/+1 counters the following turn on top of some other random PWs. I can check that off my bucket list now!

I understand most people here aren't into hyper competitive play, but i invented a weird cool broken ritual thing.

I have a Tymna Thrasios combo deck (infinite manas or Ad Nauseam or Doomsday) and i played a turn 2 Necropotence. Which is normally really really good, but i hit virtually nothing of any importance and burned a ton of life with no payoffs. I had Ad Nauseam in hand but no life draw my deck with. On my last opponents end step i cast Tainted pact. I wrote down each piece of my infinite mana combos, all 3 win conditions (Laboratory Maniac, Walking Ballista, and Tendrils of Agony). It's important not to exile your necessary cards. I knew the only out i had was not a single card but that i needed multiple and AdNaus with Angel's Grace was it. I burned through both my infinite mana combos, then Ballista, then Tendrils. My only win was reaching Angel's Grace before Lab Man or i flat lose, but i hit the Grace and Lab Man is in the deck. Phew!

I go to my turn and cast Grace and Ad Naus without using my Mox Opal and and Mox Diamond. It was turn 5 and i also have a Mana Crypt i used to cast, but was tapped out of lands.
AdNaus resolves and i have about 15 cards left in my library, put them into my hand including Lab Man and Mana Vault. We look through my new hand and we all slowly realize i have no cantrips in the pile!! With Thrasios still in the command zone it is a very pricey 9 mana to cast Lab Man AND draw a single card. I start getting uncomfortable and everyone else is sure that i cannot win.

I play a land for turn and have 3 mana. Continue thinking hard and being awkward. I tap Opal/Diamond for UG and save it for Thrasios later, my new land for U to cast Chain of Vapor targeting my Opal. Everyone goes "ummm okay...?". Copy the spell sacrificing a land and targeting Diamond. Everyone goes "oohhh...". Copy the spell by sacrificing a land targeting Mana Crypt, then copy the spell targeting my Sol Ring an opponent stole. I have nothing on board for them to bother targeting because Lab Man and Thrasios are not even in play and i have Spellskite, which they bounce anyway and i sac my remaining land to bounce an innocent token of someone else's for fun.

I replay Ring, Crypt, Diamond, Opal, and then cast Mana Vault from hand for exactly 9 mana to play Thrasios, Lab Man, activate Thrasios for the win.

Some of my most creative play yet! I love games that are puzzles to be solved and this one was very challenging. Any other sequence would have made me lose, rng could have made me lose. I had to go all in and not back down with Tainted Pact when i exiled really great cards and felt nervous.

A few Fridays ago I got my only blocker Chaos Warped away to clear the way for a would-be-lethal Kresh, the Bloodbraided swing. It flipped up Form of the Dragon, and managed to chip him down 5 damage at a time before he drew enchantment removal or fliers.

Sometimes, it's the little things.

So, finally had a game convince me to dismantle my Jodah deck. Went a little something like this:

T1 - Land (nothing too exciting so far)
T2 - Land, Fellwar Stone (setting up for T3 Jodah?)
T3 - Land, Jodah (yep!)

T4 - Land, make WUBRG, fist out a Consecrated Sphinx (table groans, indicating that, somehow, no one has removal)

T5 - Miraculously, Jodah and Sphinx survive the turn cycle, and no one is putting pressure on me yet, so I take this turn off to just play Land #5 and a tapped Prismatic Geoscope

T6 - Once again, the table fails to interact with my shit, and now it really pops off.
I tap Geoscope for WUBRG and fist an Aminatou's Augury just to kick things off.
Augury hits: Land, Seedborn Muse, Zendikars Resurgence, Ramos Dragon Engine.
Drop all that shit into play, Tap my 7 lands for 14 mana. Fist out Zacama.
Untap those lands, cast Bloom Tender and one other small guy just to get Resurgence draws.
Have 2x WUBRG floating, use it to cast Mind's Dialation and Avacyn.
Tap 5 lands for 2x WUBRG, fist out Thraximundar and then put Time Spiral on the stack.
Still have Sphinx in play... table scoops, packs their shit and goes home.

Didn't even get to resolve Time Spiral. Oh and Ramos had like 10 counters by that point. Whoops.

So, I'm playing Tomik, Distinguished Advokist landramp vs. Tatyova, Benthic Druid

Turn 4 or so: copper-leaf angel, followed by a hasty defense of copperleaf angel's abilities and mana cost.

Tatyova plays oracle of mul daya, draws an annoying amount of cards, revealing at least one to be tooth and nail.

I top-deck flagstones of trokair, start giggling, and play the admonition angel i'd been holding in hand, play flagstones to exile his general, he chooses command zone. I remind him to maaaybe read the cards i played again and pass turn.

Tatyova glares at me, plays reclamation sage on copper-leaf angel, I sac flagstones to copperleaf angel, in response he beast within admonition angel. He no longer has the mana to tooth and nail.

That maaay sound mostly like my opponent's play, but I made someone spend answers on copper-leaf angel, a card I've spent 10 years staring at trying to find a reason to include in anything, so I'm riding a johnny high right now. (Also, I managed to kill him with birds, so haha.)

I forced someone to counter my Magnetic Theft just this week. Playing Yasova, one opponent has drawn a ton of cards and is dead to the summoning sick Jace's Archivist on the battlefield controlled by a third player.
On my turn, I recast Yasova, and he is forced to kill it precombat with Force of Despair to prevent it from gaining control of the Archivist. I then play Assault Suit and cast Magnetic Theft to attach it to the Archivist. My opponent tanks for a good minute and then wastes a Mindbreak Trap on my Magnetic Theft. Felt good.