Used to describe a person you find annoying/pathetic/hopeless or just plain distasteful. Originates from a name used to describe the zombies in Nazi Zombies when you grenade their legs off.
"Bob is such a Gwinny! When he lost his ray gun, i nearly punched him."
"Dylan felt like such a Gwinny when he swapped his ray gun for a sniper."
"Savvas punched Bob for being a Gwinny about his ray gun."