Useful duck knows when he's supposed to be on deck.
Useless duck giggles immaturely whenever he's in the hole.
Useful Duck adopts forsaken Chinese girl ducklings.
Useless Duck leaves eggs in front of abortion clinics.
(courtesy of chazadillyoffdaknilly)
Useful Duck has accurate and detailed medical advice.
Useless Duck gives you beer when you have stomach flu.
Useful Duck stocks up in case of an emergency.
Useless Duck saves spam to read on rainy days.
(By way of "TimBuck2")