Burnin’ Key Cars were actually an interesting twist on the standard Matchbox/Hot Wheels car. Inside was a spring and when you put the key in it would compress it. The key would lock into place and boom — potential energy at your service.
What this commercial doesn’t show is the bored kids three days later trying to launch the cars in mid air at each others heads. Strip one of these down and you could get about a foot of air. While not the best weapon, it did briefly extend the life of the toy.