A lot of houses on my campus have glow in the dark graffiti parties-- they put black lights all over the place, and people wear plain white Tshirts and write all over each other in highlighter so they'll glow under the lights. The shirts are fun to read the morning after
My sorority did a costume blind date party at a local restaurant-- your sisters set you up with someone, and gave you half of a costume so when you got to the party you could find your date; one girl had bunny ears and had to find a boy with a magicians hat, and people with devils horns had to find their dates with devil tails, etc.
We also do a Handcuff date party where you get handcuffed to your date for the whole night-- it makes for some interesting stories afterwards ;p
*C*