Best-
by far- The Trunk Monkey
and for the local guys, the old Thomason commercials. where they are talking about the old muscle cars we used to drive "they took slightly more fuel to move than the space shuttle. I mean these cars didn't even have carburetors. just a monkey, under the hood, throwing buckets of gas into the engine."
worst-
by far, the Boots Williams ford commercials when I lived in KC. (KC guys, is that guy still around?)
or any used car commercial where some dork, in a plaid suit with his shoes matching the belt, screaming at me at the top of his lungs at 2am. does he really think that his yelling on the tv and waking me up is going to motivate me to come see him in person. if it actually got me to go to his lot, it likely wouldn't be the visit he'd been going for.