1. Mega Joker  99% RTP. Mega Joker from NetEnt has been around for more than a decade. Though it's a relatively simple game with just three reels and three rows, Mega Joker is a famous and beloved high-volatility slot thanks largely to its eye-popping 99% RTP, bonus Supermeter game, and progressive jackpot.

The Ugga Bugga slot machine game has the highest payout percentage, at 99.07%. The second highest is Mega Joker by NetEnt, with a 99% RTP. Jackpot 6000 by NetEnt and Uncharted Seas by Thunderkick come in second and third, with RTPs of 98.8% and 98.6%, respectively.