I do a lot of supersets of two exercises. I've had people carry off my dumbells that I don't rack between sets. Irritates the heck out of me since I try to maintain a 2 minute rest period and I only do 2 sets so I'm not really using the weights for long. A 3 minute rest period is a big difference and I can't tell if I'm gaining and should up the weight for the next week. I guess the most annoying thing to me is people wearing earphones in the weight room since I can't yell at them when they try to use my equipment.
Reracking weights, removing cable pulley handle and moving the pin to the top is good gym etiquette to indicate you're done with the equipment. People like to leave 45 lb plates on the bench press but I always warm up starting with JUST the bar. Helps to enforce good form as well as warming up. People rerack dumbells but not straight bar weights so I just give a cursory look around before starting to use them. If someone is using it they can yell at me but usually sheepishly tell me that they were using it or move on
I wouldn't do it if people just reracked weights.
Some old guy in the gym used to use the only 25 lb dumbells to do some cardio type exercises for 20 minutes. He was never pushing himself enough to break a sweat so I thought it was silly that he couldn't just do the exercises faster with lighter weights such as 15 lbs which the gym has many.
Grunting is a funny one since a guy in the gym likes to grunt loudly when lifting and even running on the treadmill. I got used to it and tune it out but it seriously bugs a friend of mine to the point it chases her out of the gym.
I'm guilty of doing the straight bar curls off the safety bars in the squat rack but I know everyone that does squats so I relocate. I like the squat rack because it is close to the bench where I'm supersetting with tricep curls. I don't have to yell across the room at someone carrying off my tricep dumbells while I'm doing curls. Yea, it happened. Someone else's bad behavior is driving mine. I try to encourage people to power clean weight off of the floor when shoulder pressing instead of using the squat rack because you know, the squat rack is for SQUATTING!
I was impressed one day when I noticed one of the olympic bars was bent. I knew deadlifting 405 wouldn't permanently bend the bar. Found out some genius was doing shoulder shrugs but was dropping center bar onto a bench. I suspect it was the Shrek looking guy with overdeveloped traps who also was the one that told me how the bar got bent ("by some guy"). I couldn't figure out how to delicately tell him how ridiculous he looks but did tell him his upper body is totally out of balance.
Dropping weights is annoying. Usually people trying to deadlift. One day I was not really dropping the weights but they were making some noise. One of the girls that works in the gym got on my case. I've learned how to deadlift so that I sometimes barely kiss the floor each rep. It actually makes it easier. Kind of like compressing a spring on the way down by keeping everything tensioned. If I can get the first rep in I can get the rest. Also, I don't want them to outlaw deadlifts
