First off, my apologies to you all, because this is a repost. However, I couldn't put up car-related Super Bowl ads without including it. Besides, if you missed it the first time, you're in for a treat. Pontiac aired the spot that's pasted after the jump during Super Bowl IV (Chiefs 23, Vikings 7).
The car it was pushing was the '70 GTO "Humbler," which let its driver pull a dash-mounted lever to activate the car's Vacuum Operated Exhaust (VOE) option. Doing so relieved backpressure and gave the car added punch while bestowing a positively evil exhaust note upon it to boot. After the spot aired, GM brass went nuts, pulling the commercial and killing the Humbler option itself. The spot aired just that one time, but you can watch it as often as you like by simply following the jump.