Bob Stupek, who used to own Vegas World and now it's called the Stratosphere in Vegas, had a great deal. Send him $396 and when you arrived in Vegas, you would get $800 in play money, free room, drinks and buffet.
After checking in and getting the $800, I'd go to the roulette table and put $400 on black and $400 on red. If not land on green, I'd get $400 back in real $.
On top of that, he had this other deal (coupon in the room) where you got $50 in play money. So I did that one time too. The problem was you'd get so much money every hour and it was divided into 3 increments. So I'd get a drink, gamble with his money, then go back to the room and wait. Ended up winning ~$10, but was confined to his casino.