The guy/girl who stands at the water fountain for a solid 5 minutes lapping it up while splashing it all over the already slippery tile underneath it. You're going to get a stomach ache.
The guy/girl who is on the treadmill, stairmaster, or other cardio machine who is wheezing so bad it sounds like a fire alarm. Moderation is the key.
The stinky kid in class-
The guy (usually) who stinks so bad it reminds you of 4th grade and that kid who didn't know what a shower was. I know we all sweat, but proper hygiene(sp?) will prevent it from being so bad!
The Attention whore-
Almost always a girl, purposely doing bent over rows (in the guys part of the gym, when there is a female area available), double-d's about to fall out, thong line showing through the hot-pants. (Us guys dont mind this, but I couldn't be too biased or the frog may attack
The russian from 'Rocky'-
The guy who walks around the whole time, fully flexed, and turns sideways just to make it through a doorway. C'mon dude, we know you're big....
Just a few that bug me...except for the attention whore, except for when she's uglier than sin...