Looks like a Cicada Killer wasp, a large ground dwelling, solitary wasp who's usual pray are adult cicadas.

It is the male wasp who behaves aggressively, comicality so. He is totally unarmed and harmless, however. The larger female will only defend her nest and is very loath to sting.

Good thing, too. They are said to have one of the most painful of all bee, wasp, or hornet stings. I have nothing to compare it to, but I can tell you that I accidentally stepped on one with a bare foot......youch!