Right eye. And if I'm shooting sports, sometimes I'll leave the left one open to watch the play at the same time. Kind of like a shotgun.
Funny...at first I thought I was weird for doing that but it seems common
Right eye, right handed
Using an almost same technique but it's my left eye that I'm shooting with, the right eye to partially watch the play/event. I'm not a sport shooter but this technique is also quite good for events.