I was going over to do dips (I was set to do slow, light chest dips), but two girls were on one one the dip/pull-up/ab thing, and two college-age guys were on the other one doing weighted dips with a 70lb dumbbell (they were making a good bit of noise, but not being really obnoxious), so I decided to work in with them, and I suppose I let my ego get the better of me, so I decided to do some heavier weighted dips with them instead of lighter chest dips. I let them use my belt for the weight (they were holding the dumbbell with their feet before I got there), so we all got along well, so it was fine; I did a quick set of several reps with 90lbs to warm up a little, then one of them tried it and got 1-2 reps, then I did some sets of a few reps with 135lbs. In retrospect, maybe I seemed like a gym douche to them; they were doing weighted dips with a decent weight next to two girls, making some noise, then I come in and warm up with their max, but it was all good, because they said they were going to buy one of the belts, but they were going to buy it at a local supplement shop for $60, and I told them they can get it either online or at the local Dicks for half that price, so they were pretty grateful that I saved them $30.
Also, it wasn't douchey, but some guy was deadlifting 405 with the a VERY rounded back for one painfully slow rep (of course it was to impress the girls he was with). I'm pretty sure I instinctively winced and shook my head a bit when I saw it, but I don't think anyone noticed.