Usually the life of the party. When "This Guy" (or occasionally "That Guy") walks in, you know shit's about to get good. He's liked by everyone, has killer dance moves, and just all around fucking rocks out with his cock out. He has the funniest stories, the dirtiest jokes and can swoon any lady he wants.
Usually is wearing something suave.
Occasionally could be a Garden Gnome.
This Guy: *walks into party* HEEEEEY guys!
Everyone: AW YEAH THIS GUY JUST WALKED IN!