A few times over the course of my life, in my dreams I've been very angry at my brother, and when I finally try and attack him, I wake up as I jerk my arm, or kick my foot out.

A while ago, I had a dream where I wanted to punch him, and I woke up mid-swing as I punched the wall. My knuckles were bruised for a couple of days.
This kinda stuff can happen in light REM sleep, I think.