Most impressive thing another’s character did?
I’m not impressed by other people’s characters, I’m impressed by the players.
There’s one story I heard about a guy playing a 24 hour zombie outbreak LARP who got attacked in the shower. The GM timed out and gave him the option to get dressed a bit before resuming as a zombie; he said no thanks, and just shambled about in a shower curtain with his bum out. That’s commitment.