Funny stuff..
I just thought up something else - not gym related though. This was a long time ago in college so I'm not this dumb anymore.
Friend of mine was using the phone accross the table from me. I'm messing with my roommate's blowgun which I load with a non-pointed flat head style dart (meant to scare dogs away - not sharp). He did not know it was loaded with a different dart than the large hunting style tips in the quiver.
Anyway, I point it at him and he politely excuses himself from his call and says 'Mother Fucker - I'll kill you if you shoot me with that thing' - says it real calm and polite.
So as I'm lowering the gun I burst out laughing at his comment and the dart fires, richochets off an object in the room, and tags him in the throat. He goes totally white , drops the phone, holds his throat, and says, "Oh my God, you killed me."
He figured it out by himself eventually as I was laughing so hard I couldn't talk and almost pissed myself while rolling on the floor.