I'll try to pick characters from areas they've picked from before, and also who would have good chemistry with each other.
The Players
Baby Cakes (China Illinois)
Dr. Orpheus (Venture Brothers)
Kenny (Walking Dead)
Coach (L4D2)
Baby Cakes is obsessed with D&D stuff, and can't tell fantasy from reality, so he'd end up confusing Dr. Orpheus for a vampire or something like that. Kenny also has that good old fashioned casual racism that'd create funny/awkward moments with Coach. Kenny probably would antagonize Baby Cakes and Dr. Orpheus pretty well too, but Kenny's insults would go over Baby Cake's head for comedic effect.
The Dealer
The Announcer (TF2)
Fuck you, Cube.
Bartender
Bubs (Homestar Runner)
It's Bubs, enough said.