Pansy-snook

Pansy-snook is someone who is so annoying/obnoxious, you want to smack them as soon as they enter the room.

Etymology:

pansy |ˈpanzē|
2 informal offensive an effeminate man.
+
snook 2 |snʊk| |snuːk|
noun (in phrase cock a snook) informal chiefly Brit.
place one's hand so that the thumb touches one's nose and the fingers are spread out, in order to express contempt

Man, that Gunther kid is such a pansy-snook, I can't stand him.