I also do small give-aways based on attendance and activity outside the gym. For example, I have one coming up where people will get points for being active, going towards a raffle for some group sessions with me. More details after I launch the promotion, but it’s not public yet.
In past years, we did attendance contests and gave away a one-hour massage, two one-hour training sessions, and a free suntan. That went OK for the gym. The one I’m doing is targeted more directly towards people attending my classes, tracking their success, and strengthening their bond with me as their trainer.