Quite a few things about my gym annoy me:
1) People who take the heaviest fixed weight barbell up to the studio and don't bring it back, so if you want to use it you have to interuprt a class, take it trhough 2 fire doors that open towards you (so you can't just push them open with you body or foot) down a flight of stairs and through a third firedoor before you've even started the exercise. You're kanckerd before you've even started. Inconsiderate pricks.
2) People who use two benches to place a barbell on to do dead lifts, especially during peak times. That means there's now 3 peices of equipment that no one else can use so that one person can do one exercise. Why do you even need those benches? If you can't lift the barbell off the floor then it's too heavy. Stop down a few KG's and let other people use those benches you don't need, you inconsiderte prick.
3) People who take 3 or more peices of equipment at once, like 3 fixed weight barbells, and who then don't offer to let you go in between as it were and use the item/s they're not currently in the process of using when you ask them if they're using them all...again, especially at peak times. You're just hogging equipment other people want to use, you inconsiderate prick.
4) People who use the same piece/s of equipment for stupidly long periods of time during peak times. I mean do you really need to spend over half of your entire session doing your biceps and only your biceps? Other people have paid to use that stuff too, you inconsiderate prick.
TL;DR - I hate inconsiderate pricks in the gym lol.