How do you fist fight in Skyrim?

Answer 1

You can fight at any time with your fists if you deselect any and all weapons/shields you were using. You could keep one in one hand, but don't attack with that hand, because it will use the weapon rather than the fist. Otherwise, sometimes when talking to people, you can challenge them to a brawl if you need something, and if you beat them, they will usually give you what you need.

Answer 2

Select unarmed and push what you normally would push to shoot a gun. You can counter if you push (X for 360, or square for PS3) at the right time.