I'd pick chess because I used to play a lot and actually played against some chess masters and won. It's been a little bit since I've played, but it all comes back to me every time I play. If I could get them to agree to hold off on the killing until the game is done, it would also give people a chance to plan something on the chance that I lose.
I'm not saying it would be a definate win, but I'm fairly confident. Although Russian Roulette has a one in six chance to kill me, with the odds of killing me growing greater with every squeeze of the trigger. Granted, they would be facing the same odds, but I'd rather gamble for my freedom on a calculated risk instead of mere chance. It's not like I'd have long to regret my loss if I did lose.