I usually use my Colt Python revolver. I play with one shell with BB's in it and spin the barrel and snap it in, not knowing where it is, and then rooster it and then shoot it at my stomach, and then hand it to my friend and he repeats. It's really fun with 2 - 4 people. Try it sometime.
Note:
I know in real Russian roulette you aim for your head, but it's too dangerous and it can cause brain damage.