Someone that enjoys smelling other peoples' B.O.
Person A: Why is Rob smelling James' soccer shirt?
Person B: Man, what a funky junkie.
A person that is very conscious of where his appendage is hanging (left/right/centre)
A: Hey ... uh, why does Lucas keep putting his hands in his pockets like that?
B: Oh, right. He's a Sacktracker, Davo.
A: Ah Shizzledizzle.