Oh, roleplaying stories, I have a bunch of those, but for many of them you probably would have had to be there to find them as amusing or funny as I do.
In a Feng Shui game I once ran we had one of those exploding dice moments when a mook (i.e. cannon fodder) stabbed a Big Bruiser (i.e. a 'tank' who can take more damage than anyone else in the game). For those who don't know FS, you roll two d6, a positive and a negative die and add or subtract the result from your skill. 6s are rerolled. The mook needed at least a +2 or +3 result to just hit the Big Bruiser. Every point above that would result in a point of damage. While the Bruiser was still laughing at his puny opponent I rolled, and rolled, and rolled ... In the end I think I did him around 35 points of damage. Must have rolled six or maybe seven 6s in a row there. To the day I still can't quite believe it, but I do have witnesses.
Another fun story happened during a Fifth Age Dragonlance game. In that time of Dragonlance history magic items are rare and making new ones was pretty much out of the question. Due to some time traveling the players end up in an earlier period of history when magic items were far more common. There (then?) they face this sorcerer who had just opened a portal to a demon dimension that manifested as a big hole in the ground. The players attack with bows and arrows, someone throws a few spells at the enemy, and one player who had control over an earth elemental sends his elemental into the fight. In the end they manage to knock out the enemy, but aren't yet certain if he is dead or just unconscious. The player controlling the elemental, still pretty much fired up from the fight scene, orders his earth elemental to pick up the sorcerer and throw him into the hellhole, just to make certain. Everyone cheers. The enemy is dealt with and now they can go home to their own time. Until ...
Until someone realized that they have just thrown the biggest stash of magic items they will ever come across in their lifetimes into a hole to hell, right before they are whisked back to their own time.
Oh the look on their faces. Just priceless.
I remember a similar story where in Forgotten Realms, a party ended up meeting Ioun himself, maker of the Ioun Stones, selling them for a pittance. They loaded themselves down with the suckers-yeah, they won't last when we return, but we have them for now, damnit!