It's not easy to think of specific parts, as opposed to the whole. But it's true that my immediate attention is drawn to the upper arms, shoulders, and chest. Especially a nice hairy chest, which can make me a bit weak in the knees.
There's also that dimple on either side of the ass that you can see only when a man is standing or lying just right. Grrr. And a good strong back is totally sexy. And, of course, the ridge of a man's cock head, pushing up against his trousers. Hairy legs.
Okay, obviously it's the whole shebang. I can't choose but one.