Need help identifying a science fiction movie I believe to be from the 80's. In the movie, a girl swings a sword at an alien. The alien starts to laugh, and it is assumed that the swing missed, until his head slowly starts to slide off.
I remember this part of the movie from when I was a kid. As soon as this scene ended my parents made me change the channel. It has bothered me for years trying to remember what the movie was.