The reason why I said chest, shoulders, tris, and bis, is b/c a lot of people, for some reason, think that bench presses work the biceps.
I think that the one-arm pullup is a showoff move. I mean, nobody is realistically going to do sets of one arm pullups, they're just showing everybody in the gym that they can do them. I can do a one arm pullup with the slight assistance of my other hand grabbing my wrist. But I certainly don't do them for reps.