Geriatrics
I understand that y’all have been roaming this planet for decades longer than have I.  That fact does not give my senior friends a right to monopolize 6 different areas of the gym and shoot me a stink eye when I have the audacity to invade one of them.

Man in the mirror
The man in the mirror guy has decided that he will complete his curls [or another dumbbell exercise] directly in front of the weight rack, such that he may watch every muscle fiber engage as he blasts out his reps.  Never mind that he is standing in the way of other members’ access to 4 sets of free weights.  Move, clown.

Who let the dogs out
There is no doubt that most folks go to the gym in the hopes of becoming shredded.  Bro, keep your shoes and/or socks on when squatting.  Banging out the sets in your dirty socks, or worse, in your bare feet, isn’t going to transform your physique into that of Mr. Olympia.  It is weird and disgusting.  Keep your Asics on.  Otherwise, invest in a pair of those strange-looking shoes with individual slots for your toes.