Scun is the 60's LA Hell's Angels term for brown sticky highly potent bath tub methamphetamine. It is the only form of meth that is strictly injectable, because of its consistancy (A.K.A peanut butter dope). The term is associated with the slam a gram ninja clan (notorious for shooting up whole grams in one dose). Scun is also a sludge metal(bongzilla/eyehategod-esque) band from Arkansas.
Ulzzang true definition is "best & "face" = best face in korean. They are basically people with above average looks, sometimes with the use of photoshop and haduri who post their pics online, some becoming internet celebrities.
"Hey, see that chick over there? She's pretty enough to be an ulzzang. :D"