The ones that get to me the most are the ones who do strange "exercises" and grunt the whole time. I had some older guy (~40) stand between me and the mirror (thanks asshole, I wasn't trying to watch my form or anything) rocking 45lb DB's from left to right in his hands...it looked like he was trying to swing them up for curls. He did this for 6 reps, grunting the whole time, then as he put them down he was like "ohhhhhhhh man..." and smiled at me Grunters/yellers also get to me in general. I constantly push myself in the gym, yet you'd be hardpressed to find me grunting/yelling. If anything, I exhale loudly towards the end of my set, but that's about it. Granted, if they're lifting a lot, I don't mind.