A combination of skell & scumbag. One who possesses the qualities of both. This person is generally a low life who also doesn't hesitate to back stab his friends.
Bezzy: Can you believe he fucked Tim's ex-girlfriend right after they broke up and then stole $20 from her purse for crack money?
Carts: That's ridiculous. I thought they were boys and all of a sudden he does that. What a skellbag.