Memorable DnD/ Tabletop RPG moments?

What are some of your most memorable moments from a tabletop RPG game session? For me its easily during a campaign I was in awhile ago my DM had a whole forest maze type thing with traps an shit that we were supposed to be chased by a werewolf pack through. Instead we found a pit trap and decided to push the werewolfs in the pit. It worked as they couldn't climb out.

The only time I got into a tabletop session I was an annoying dickwad, so I got kicked out. Good riddance!

A friend of mine a while back ran a small campaign through Roll20.

My character had some small magic item that allowed him to change his size, and at the time I was considered large.

In some rich dudes house that we were invited to stay at for plot reasons, there was a piano, which my Human Fighter decided to try his hand at.

I rolled performance and got something low, not passing the check. I told myself it was because I was too big and shrank myself.

Rolled it again and barely passed. Seeing how it was one of our first campaigns, and my only experience before hand was shitty internet stories about bad DM's getting fucked over by their players and stuff, I didn't find myself fully satisfied.

Shrank my self to the small size and tried again. Perfect. Fucking. 20.

Friends had a laugh, and was one of the few times the dice helped with our shitty jokes.

There was this one time I spend a few days writing up a very specfic npc, who was secretly the brother of one of the elven player characters and would move the plot forward by revealing that he was actually a drow. And I detailed this guy quite extensively, full backstory, rolled all his stats, did all his classes and spells, equipment, everything. Because he was going to be a major recurring character, I would need all that background to play him and improvise as necessary. But things, well, things didn't work out.

So picture the scene, if you will. The party have returned to their base of operations, a small town on the frontier. But it appears abandoned. Some buildings have been burnt down, there are signs of fighting. Something bad happened here. And at the town center, they encounter a lone elf, his white robes and silver armour splattered with blood.

Now at this point I had intended the npc to open his arms and say, "At last my brother we meet again." Pass a hand in front of his face, removing his magical glamour to reveal that he's really a dark elf and smile, saying, "These poor people. They thought I was you."

I thought that would be a nice dramatic way to introduction this antagonist to the story. But the party's cleric had other ideas. Oh, yes. Because before the npc has said a single word, the cleric player says,

"I step forward and cast Plane Shift on him."

Ohhh... what does that spell do exactly?

I look up the spell.

"Well ok, but this guy seems alert, you'll have to roll initiative for that."

We roll initiative. The cleric wins.

"Well, I see here that this spell requires a touch attack in order to..."

The cleric rolls a natural 20.

Ahhh..... Wait, saving throw. I check the spell, yes there's a saving throw, great!

I secretly roll the npc's saving throw. He fails.

Of course, this guy is really a Drow, he has innate magical resistance!

I work out the modifers for his magical resitance, and make the roll, again secretly because the players won't know about this. He fails.

Son of a bitch.

So in the end this guy opens his arms and says, "At last my brother we meet aaaggggggrrrrrrhhhhhhhh...." and promptly gets sucked into the Elemental Plane of Fire, never to be seen or heard of again.

we were interrogating a drow that we had captured, and this one dude in our party decided to just light her on fire for no reason

everyone was pissed

Well, our GM recently posted a list of crimes to hang on our group (about 80% of this is attributed to one member, not me, now the epic fail at saving a Goblin, that was me XD)

Heroically saving a friendly barmaid from a zombie, by knocking said barmaid out 
Defending a friendly goblin by stabbing it in the head
Forming a cult- the Church of the Fonz
Massacring said cults followers....twice 
Running away from a divorce lawyer
Turning one of their "manhood's" into a crystal 
Turning one of the party into a crystal
Killing a friendly sleeper cell
Throwing a dart into a child
Necrotic puppetry 
Chicken farming
Selling "alcohol" without a licence
The smartest member of the party being a dog
Defiling a friendly Kobold
Attempting to sell a party member into indentured servitude
Selling a party member 
Insulting powerful Drow 
Attempting to create an "arse based flame-thrower"
Spending the night in an all male brothel
Attempting to befriend a zombie dog
Aiding, abetting then hindering bank robbers
Attempting to slight of hand a giant hostile Crocodile 
Assault 
Embezzlement
Selling Half orc piss as part of said embezzlement 
Poisoning – themselves and others
Desecrating several corpses
Identity theft 
Normal theft
Turning themselves into a potted plant

The party I'm in right now was recently tasked with stealing a sealed envelope from a guardhouse. I came up with a near perfect plan for my character to magically disguise herself as a guard and cause a distraction for the other guards in the building so I could walk right into the office and take it. Low chance of failure and unless something went catastrophically wrong they would have absolutely no idea who their suspect was. Naturally, our artificer thought there were too many dangers for this plan not working so he wanted a contingency in case I somehow failed (though the way I saw it, if I'd failed then it would be best to just abandon the mission altogether). He and two other party members hung out on the roof of a building next to the guard house as I executed my plan and got away without a hitch. Of course the guards start searching the area, I'm already long gone but now there's a tiefling standing on the roof next to the guard house for no reason and he failed his stealth check (the other two succeeded and got away).

The first thing he does when they start questioning him is implicate another party member who himself had nothing to do with the plan since he refuses to break the law (though is nice enough not to try stopping us). The guard, frustrated with his attitude (YOU'RE BEING ACCUSED OF A CRIME, STOP SASSING THE GUARD!) tells him to wait in the guard house for the Knight Captain to arrive. So he sits at the reception desk for eight hours until she shows up, and she is confused by a random civilian sitting at the reception desk and tells him to just leave since he obviously could not have committed or aided in the crime (both of which were technically true, the alibi he gave was his friend told him that roof was a good place to go stargazing). My familiar was with him so I could hear the things he said to the guards and we got in a heated in-character argument that the local bartender could definitely hear. Fortunately he saw it more as free entertainment than something to report to the guards.