I hate that the Health field for func_button's default to 1. I always forget this and get really mad, trying to figure out why my buttons aren't doing anything.
It's the best when you have a big map on a final compile, and after waiting for the thing to finish, A stupid compass setting is in the wrong direction, after you thought you fixed it twice. After may painful occurances of this, I now triple check the compass settings/flags are correct.