Tough one, largely most great gaming moments I find are of the "you had to be there" variety. However what I am particularly pleased with was this visaul aid I perpared for the players in advance of the final showdown of my Necessary Evil campaign. By then there were so many factions and moving parts it could only be summed up graphically. Also, drawing is fun.
One time The PCs encountered a very hungry man on a lonely stretch of road and fed him, but he kept asking (very politely) for more and was insatiable. They concluded he was undead but he didn’t know it, and decided that eventually they’d run out of food and he’d need to eat them. So first they tried Demonstrate to him that he was undead - I’m not sure what they hoped to achieve by this but he never really got it. Then they tried sending him away, but he kept coming back. Finally they dismembered him (all the while him being very polite) and put his parts in a bag, which they were later advised to burn.
Then there was the time they ingratiated themselves with a caravan leader so they could share his caravanserai for the night, and he invited them to a feast at which he got drunk and made increasingly magnanimous gestures. Well into the wine, he bragged he could sever the neck of a camel with a single slice and he pulled out a very large scimitar. There were some polite protestations but he proceeded to try and the PCs laughed and placed bets. The merchant wasn’t able to quite do it, so he decided to double down and bet that he could cut off the heads of two slaves in a single blow, and pulled out an even bigger scimitar. This was too much for the guests, but they didn’t want to lose face by objecting out loud so instead they discretely started a fire in the tent and all hell broke loose. The following morning it was all hangovers and bashful apologies by everyone involved.
The best scene I have ever seen in a game was the dual execution scene in my Game of Thrones game. It worked so perfectly - one noble executed for accidental fraticide screaming his innocence, one member of the PC family executed to keep a family secret. Parallel scenes at the end of an intense session and a silent table at the end. Nice.
In another session, exiting their first dungeon on Symbaroum like the Scooby-Do gang running from the monster and bursting out of the door with tentacles and thorns and darkness chasing them. Ashen faced gamers...
Mine still remains the climax of my standard Dr Who scenario where I let players play anyone from anywhere in Time and Space (as long as they’ve never been on the TV series.)
Brilliant player who - as far as I know - I’ve never seen before or since. Played a Speedster superhero called Quickstep. When the J’Hdun nuked the big bad from orbit he rolled high on the dice and was the only survivor as he outran the nuclear conflagration.
As one, every other player turned on him and shouted - “Quick! Run round the moon, really, really, fast and turn back time!”
Impossible of course. But he rolled and guess what.......