Sweet Bonanza by PG.
Everyone knows this slot game and it's something that is generous when it gives out a max win. If it's not, then it's a snoozefest and you are guaranteed to get your funds drained. I once played the said slot game with my remaining $100 and thought I could be lucky knowing that it has been giving me constant wins for some time now. Lo and behold, in a matter of 30 minutes and a bet of $.50 per spin, I drained my money immediately. The next day, I went back and played it again for $50 only to lose. Idk, there's just something to this game that keeps me coming back even though I know that I will lose again.

Probably Gates of Olympus. I've never made any profit from this slots game, but for some reason I enjoy playing it. Maybe it's due to the greek mythology theme it presents, although I don't have any expectations of winning big from it someday, as I know slots is one of the worst kinds of gambling games to play aiming winnings, since we don't have much control over our gameplay. The settings are limited and you are always on the hands of the algorithm.
Damn, this game is also a money sink. I think I downed a thousand dollars to this game in a month because the mechanics are pretty easy to win big. It's that false sense of 'easy win' that caught me by surprise and get me losing a lot of money in a short span of time.