For my own, here are a few good ones:
(1) A Half-orc Fighter, after helping set up camp, goes to hunt for some meat to roast. He has an sword. A Bastard Sword. That's it. Comes across this deer (in fact, it's a Sianach, a demonic, man-eating deer from celtic folklore/mythology) with weird, red eyes which has the occasional puff of smoke come out of it's nostrils. Runs up to it and attacks it with his asword. Deer just stands there, looking agitated as the half-orc runs up and rolls a CRITICAL FAILURE! He sinks his sword up to the hilt in the loamy ground, and deer kicks the living crap out of him, making him run up and hide in a tree. Eventually, a few hours later, the deer leaves and the half-orc goes back, shamefaced to the camp, sans his sword. He asks if anyone will help him dig it out. The dwarven barbarian, quite drunk on ale, throws him the shovel from his pack and tells the "stupid pig-face" to "go dig it up yourself!"
Another hour later, and the half-orc finally gets back, sword in one hand, shovel in the other a respect for that weird deer in his heart.
(2) Later in the same camaign.... had a guy who had played D&D in the past with one of my players come into my game, which is a low magic, dark ages-like setting. The party has been assaulted by a weird deer again, and he is a traveller with a massive sword who helps them out defending from this odd creature. Anyways, some woodsman come along and we repel the deer(/Sianach). We get led into town, where this traveller (a human fighter) says he is going to go to the mayors offices. I say "sure". So, he goes in there and starts asking about where he can get magic items. Low magic campaign setting that he's been aware of, and he does that. The mayor is spooked and calls for his guards. They arrest this guys PC, on accusation of witchcraft.
Then the mayors guards with the town guard go to the inn the rest of the players ar staying at, thinking the new PC is 'with' this adventuring party (for now they just know of each other and after a few days in town the plan is they are going to merge and come together in a bigger party), with only the half-orc still suited up for war. Standoff in their room, with the party proper promising to leave right then and there without further bothering the townspeople. Mayor says that this traveller should be hanged by the neck, have his throat slit and then burned for witchcraft, and the party agrees, not really knowing anythign about this oddball who has gone sniffing around for magic items. Party is ushered all the way to the city gates and meets up with the party's Priest of Nyaricus who has been staying at the temple of Narkus (another name for the same deity, but in different regions) and says "hey, where's that new guy?" Half orc says: "Oh, he's
hanging around town someplace, probably some
hotspot or another."
A classic among our group
(3) Played in a campign with another standoff in and Inn and the party's cleric 8/fighter 2 runs straight into melee and then doesn't heal anyone, or himself. Dies without having cast a single spell. Idiot. (and the person playing the PC was a jerk, too).
(4) a really old campign which I was playing in had me as the Dwarven Fighter in spiked fullplate with a battleaxe and shield (favourite character to play, BTW

). We are underground someplace, and come to a stream 5' wide.
ME: I can jump across this, easy! *rolls* Made it!"
DM (a RBDM if there ever was one): okay, in the middle of your jump the gaint crocodile jumps out of the water and snatches you in its jaws!
Me (automatically): "how in the HELL dos it fit in a 5' wide stream?!
DM: Oh, actually it's wider than that, 20' feet or so
Me: What in the hell do you mean, '
it's 20 feet!!" You said a second ago it was 5 feet wide!
DM: Yeah, but youre right: the croc would fit in that *smiles eveily*
Me: Well, that's not fair - I don't want to be eaten by the croc!
DM: okay, fine the croc doesn't eat you - but you did however fail the 20' jump check acrocc the stream!! *evil smile*
Me: What?!?!
DM: You are now sinking to the bottom of the river.
Me:
DM: *rolls* huh, the croc now spots you sinking down
Me: AHHH!!
DM: he bites you again, and swallows you whole.
Me *steams*
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THAT one pissed me off, but he was a Rat Bastard DM, so w/e.