Pikachu: My best in Melee. I've heard he has received buffs, so I look forward to that. Plus I think hes cute.
Pit: Seems hard to master, but has amazing recovery and those arrows are good against edgeguarders. He can also be very defensive when he needs to be.
Spoiler Alert!Lucario: He has impressive range on most of his attacks. He is also a good at combos, and can wall cling/jump. His specials are situational, which can be useful when mastered. Last but not least is his unique ability to deal more damage and knockback, the more damage he has.