I have a lazy eye, and normally look at everything through my left eye.
I shoot right handed, but when shooting handguns I sight with my left eye.
However, when I am hunting I have to put a patch over my left eye to force myself to use my right eye all the time. Otherwise I see a tasty critter, raise the rifle, and then lose sight of said critter when I switch eyes to sight down the rifle barrel. This isn't so much of a problem with larger critters, but it's a show-stopper for squirrels, especially in the early season.