One of my all time favorite commericals would have to be the "Snicker's" commercials, where a hoard of elephants invade a newstand and make off with a trove of Snickers bars, and one vendor says to the other "He didn't pay" and the dead pan response from the other vendor "They never do."

As for the one I really hate, the one with the geek in the glasses and funny suit (can't remember his name) trying to sell you a book with info on where to get all sorts of government grants and free funding for projects, etc. Someone should open a trap door beneath him 1/3 of the way into the commercial.