Zippy Ziggy - The protagonist is a lying, two faced selfish bastard. He will fight only as a last resort and is pretty happy to let others suffer in his place. The only exception is the girl he cares about, he gets quite heroic (and will lie to appear even more so) when she is involved. Not to say that he won't go and make someone else do all the hard work and then swoop in and steal the spotlight.

Kyou kara Ore wa!! - Mitsuhashi is, hands down, the best shonen lead ever. The other manga by the same author is also fairly similar (some would say a sort of re-imagining). It basically deals with a delinquent duo where the one guy (the leading character) is, for lack of a better term, an asshole. Most of his panel time is spent aggravating, mooching, tricking, harassing his "friends" (better to call them victims). The rest is about him beating up guys that are even worse than him, getting even with anyone and everyone that he even remotely thinks is aggravating him and, when fate decides to be cruel to good people, him trying to be a good guy (with predictably horrible results).