Things that were a hit:
Personal Misty Mate misters
Beach bags-everyone used them
informational booklets (we made a brochure on Vistaprint with all of the events mapped on the hotel map)
Self addressed and stamped postcards with a request to send your favorite memory (this was a sad one...was hoping to get them all back and make a book...only got 5 back). Glad I didn't sub this as the guest book as I originally intended!
Key card holders
Cups for drinks (the hotel cups were large enough)