Blue in first place with Bianca in second and Brendan/May in third
Blue - bland and flat character. And the "Smell ya later!" catchphrase, it's funny the first few times but it gets old real fast. Not to mention, he's an ass. Granted, so is Silver but at least he develops over the course of the game.
Brendan and May - Utterly forgettable.
Bianca - yeah, her ditziness got annoying really fast.