To get conference attendees to stay until the end, and return program evaluations, raffle tickets were given in exchange for completed evaluation forms. Raffle drawing was last part of the program. Definitely seemed to work - many holding up evaluations to get a raffle ticket. Five or 6 prizes (e.g., golf balls, box of chocolates).
Man at my table won, but didn't want to go to front of room to get his prize - so I (reluctantly) said I'd get it. Resulted in getting my name announced and picture taken. Prize: White House Christmas ornament featuring Grover Cleveland's wedding. Dozens at reception afterwards congratulated me on my "win".