Gene Hackman
Now I'm the 1st to admit that my ability to recognise actors in any given movie is poor at best, but that has to be Gene Hackman playing one of the perves who abduct young Dave in the beginning of the movie. Trouble is, I can't find any list of credits to confirm this.
I think he might have done a cameo to help his mate Clint out.
It's Gene, isn't it?