What opening would you use is you were playing Magnus Carlsen the best chess player of all time?

"Mangus Carlsen the best chess player of all time?"

No such player.

1. e4. What else?

Arguably he might be, having the highest rating of all time and all

Kasparov got to 2851.

I think his point was that his name is spelled Magnus, not Mangus (As in latin for great: http://en.wikipedia.org/wiki/Magnus )

ManGus is an awesome name. He sounds like he's almost a superhero but not really, so he's a cool guy to hang out with (unlike those other jerks who feel like they are better than you, just because they fly and fight crime).