Russian Roulette Rimjob
While lying naked with your partner in the dark, you each slide one finger in to each others rectum without your partner seeing which finger. You then each pick one finger on your partners hand and suck on it and continue this until someone picks the wrong finger (the rectum finger). The person who get the rectum finger first, loses. (also known as RRR)
My girlfriend and I played Russian Roulette Rimjob and she got the shitty finger on her first try!