Let's see...why I wear a hat and what do I wear when I do. Well, for starters it helps the mask fit more comfortably, and the more comfortable you are, the better you can think. Secondly, it absorbs sweat so it doesn't get on your lens and impair your vision. Third, it's another bit of style and sponsor space, so naturally I'm all for that. Forth, it's something paintball related that you can wear all the time off the field and be able to think about your favorite thing to do. Fifth, it's something to cover up how crappy my hair looks on and after game day. Oh, and I like the usual reasons like bounces, etc.
I wear Animal head bands and hats the majority of the time, my Middlesex University cap, occasionally a bandana, or miscellaneous others if I find them to strike my fancy at the time.