What
Winning too much, at the amount you usually spend per spin I am surprised they notice!
I think the "Holy Grail" of beating the odds actually exists, Fruit Machines are littered with these Chalices of fortune. With casinos, the "Holy Grail" is usually the inept Marketing Manager; however, the Wizard makes reference to a few games that once had an expected return of more than 100% in the early days. Cryptologic "Double Bonus" was the most recent, however it was the Comp points that tipped the balance. MG are turning out new games with renewed vigour, and one day I am sure they will slip up to produce a promotional combo with more than 100% return WITH AUTOPLAY!
I have already seen "Double Points" on MultiHand Vegas Strip, and "Triple Points" on Vegas Craps of all things. These are at casinos that normally comp at 0.1% on all games, so 0.3% on Vegas Craps is risky even allowing for "no risk" bets not counting. 0.2% on Vegas Strip reduces net house edge to 0.16% and players earning 30,000 comps in a month get 25% extra! (Dropping net house edge to 0.11%). Mind you, it's 150x D+B on any bonuses used for this!