Gonzo prestige classes are those that come from the Gonzo line of books.
Impersonator: Impersonators are characters who play dress up and pretend to be heroes of old to try to gain some of their power. The closer in likeness they are to the original, the more their power grows.
Living Bomb: Some people are so full of energy, hope, love, or whatever else that they could just explode! Living bombs take this idea literally and can spontaneously combust by overloading their bodies with arcane energy.