This one always makes me laugh..
It's for A&W Rootbeer, and this guy is getting interviewed for a new job by a guy named Mr. Dumass. The guy keeps saying, "Mr. Dumbass, I will be an assett to this company, because, Mr. Dumbass..." and the boss cuts him off and says, "It's 'Doo-moss." and the guys' eyes pop wide open. The next cut is the boss guy shaking his head and saying, "What a dumbass!" I've only seen that one on MTV.
My other favorite is for Finish Line I think, where the guy is jogging and the Finish Line worker comes running up next to him with a boombox playing that song from Rocky, and the jogger pushes the guy and he falls flat on his face. I laugh so hard at that one, every time!