Two quick stories:
A) In a 2E D&D campaign I'm running, my friend Matt makes a half-ogre grappler named Tahnk. Grapples the heck out of everything, much like the luchador above. One day the party is wandering through the wilderness, and sets up camp. Tahnk's player has been drinking all night, he's getting a bit silly, and becomes very insistent that his character is wandering off alone to "do his business." He's being really dumb and wants to "role play it out!"
So I tell him he finds a nice bush to stand behind, drops his trousers and is about to do his business when an OWL BEAR rises up from the other side of the bush and roarsqwaks at him. We spend a couple of minutes debating what a roarsqwak sounds like exactly, and then resolve the combat. Tahnk is able to successfully grapple the owlbear before it can attack. Using the 2E grappling tables, we determine that Tahnk has the owl in a full nelson. He maintains the hold until the owl bear passes out, screaming for help the entire time.
The party successfully hears him, comes running, and arrives just after the owl bear passes out. And I smile and say "You come over a slight rise, and in the clearing below you see Tahnk standing in a bush with his pants around his ankles. Directly in front of Tahnk is an unconscious owlbear. Tahnk appears to be holding the owlbears arms back and grinding his hips against its rump. You're not entirely sure, but he appears to be [CENSORED] the owlbear."
For the rest of that campaign whenever the party needed to intimidate an NPC, they would point to Tahnk and explain that this guy was so tough he [CENSORED] owlbears, and Tahnk developed a reputation throughout the land for being a degenerate owlbear [CENSORED].
2) Beta Playtest of Pathfinder, running the Dungeon Crawl Classic adventure Castle Whiterock. My friend Eric is playing an Elven Cleric (forget his name). The party is fighting a few orcs, enough that there is one per player. Eric is getting beaten up on pretty badly but due to the layout of the tunnel he can't move out of harm's way. He attacks the orc and gets a critical hit. We're using the critical hit deck, and he gets a really awesome Bleed damage result and leaves the orc staggered, but the orc doesn't go down. It's going to get in another attack before it dies and Eric knows it. But it is definitely going to die from the bleed damage right after that.
He begs the other players to break off from their fights and come kill this orc for him, so that he doesn't go down before he has a chance to heal himself. Everyone asks how many hits points he has (metagaming, but I allow it), and then starts teasing him for being so concerned. The other players all decide not to help him out, promising him that he'll be fine, and the worst thing that could happen is that he goes into negatives. One player actually says outloud "There is no possibility that you'll die."
I go to roll the orcs attack. Eric says "He'll get a critical hit." I roll, natural twenty. Eric sighs and says "He's going to confirm." I roll, natural 20 again. Eric grabs his character sheet and crumples it up. The damage is 3d12+24. I roll a 12, 12 and 11. Eric's character has 12 hit points and a 12 Constitution, which means the orc takes him to -47 HP, a good 35 points past "Completely Dead."
Everyone else at the table just sits there silently as Eric fumes. I felt so bad for the guy, but at least it wasn't my fault -- I'm not the one who decide to abandon him to fate, like the other player's did. They all felt so guilty. Just the worst thing I've ever seen happen to a player.