I'm gonna have to say Randy Ortons punt.
Sure, I know. It hurts and it could knock you out getting kicked in the head, but look at how many superstars actually do kick their opponent in the head.
You're kidding right?
Orton's punt has impact, he stands back and starts running for the punt, even when it's badly done it looks painful.
When the other wrestlers kick eachother in the head they don't take a stand back to run for the impact, it looks a lot more like a stomp, or what would have to be an Enziguri, Sweet Chin Music or Trouble in Paradise, two of which are already finishers so they can't possibly count on your theory of "look at how many superstars actually do kick their opponent in the head"
Besides, the punt serves as a finisher, while a few people use the spear (Batista, Big Show on occasions) neither of them served as a spear, Edge's spear does serve as one, hence it should serve as a match ender more than a simple move.
And to top it off, as far as I've read Triple H commented on the impact of the punt, that it actually does hurt, leaves a stinging feeling in the neck I believe he said after he was punted at Backlash, so something that legitimately can leave your neck stinging doesn't have the ability to come off as a powerful finisher, I'd call you nuts.