We're doing a bachelor/ette party (both together) and have pretty much settled on doing a scavenger hunt that ends up at the restaurant or something. Just a couple of considerations: we don't want to make the teams spend a lot of money (we're thinking of getting two $20 visa cards or something for them to use) and we want a mix of pictures and things so we can make them a scrapbook.
Oh and if it helps, the party is on Friday the 13th and the wedding is on Halloween, on a haunted aircraft carrier. We're thinking of sending teams to the haunted house to get an autograph from one of the ghouls that works the lines. Dorky? That's the kind of stuff we need more of!