I went to gyms for a long time, long before they became fashionable from 1986 onwards, when there were only about 3 gyms in the whole of Brighton and Hove. I was never into big weights or bulking up. It fizzled out once we had kids, I was keen to see to see them after work, rather than getting...
Hogging a machine, even during very long rest breaks. Used to go to Corals Gym years ago, where a group always hogged the Smiths Machine each evening, no one else got a look in.