It's hard to think of Sea World as a scary place. The seals can be moody sometimes, but not scary. Nevertheless, they promise a good time, with a bunch of Sea World employees hiding around to jump out at you. Maybe they'll get the fish in the act also. Okay, maybe that's going too far.
Costume parties are cool and quite popular around here.
If you need something quick and easy, get some makeup and some fangs, and you've made yourself a vampire. Those contact lenses that are all black and yellow are awesome, but you better have some money to spend for them. If you dress up, don't wear a white trash bag. That got old quick. Dressing up as a cop isn't a great idea either.