"I told you once, you son of a bitch, I'm the best there's ever been."
For quite a few reasons.
* The speaker is a boy. A child. And he's saying this to the Devil himself. That takes balls of adamantium.
* This is the only song I know of that doesn't curse liberally - it just drops one big B-bomb right at the end. And it is awesome.
* Irony. It's a display of pride, which is (supposedly) the worst of the Seven Deadly Sins. The Devil might be thinking "ah whatever, I'll have his soul in 80 years or so anyway".
* Then again, the pride is completely justified, because he just out-fiddled Satan. St. Peter will probably give him a pass on that.
* Did I mention that it's awesome?