I had to use a bathroom at a restaurant years ago when I was hit by a random stomach ailment. Like most people I'm sure, I hate using a public crappy, but when you have to, you have to. Anyway, this random guy walks in and starts prying at the door. He may as well have been using a crowbar. He essentially broke the door open and then yells out "oh what the hell man, lock the damn door". It wasn't a weak lock either.
And one pet peeve for me: people who are using the urinal and start ripping off loud farts. I know you're in the right room for that, but at least wait until the room is empty. We have a small 1 stall/1 urinal bathroom here at work, so 9 times out of 10 you're the only one in there.