Eranilor Nailo - Elven ranger/rogue/deepwood sniper. I played him in a RttToEE campaign, and he's the only character I've played whom I explicitly set out to model on my own character and personality. Maybe because that's such a change for me, he turned out to be a delight to run. He was a retired literature teacher turned bounty hunter, had an idiosyncratic and iron-clad moral code that he'd formulated, was intensely cynical and completely optimistic at the same time, was completely unflappable, would eat anything that moved, read plays and poetry to relax after a hard day killing things, and saw the humor in just about everything. Eranilor was the only PC in the group who went through the entire RttToEE without being killed, remaining thoroughly unconvinced all the way until close to the end that the PCs were involved in anything world-shaking. Quote: "What do you think this is? Some kind of an adventure story?"
Kane - Warforged Bbn/Cleric of Fharlanghn. Currently being played in a Savage Tide AP campaign (PbP), though it's not an Eberron game. He's an amnesiac, who was found by another PC floating on a piece of wreckage from an unidentified ship, and has been trying to work out who/what he is ever since. Thus far, what he's discovered is that he was probably constructed many centuries, if not millennia, ago and that he somehow has an affinity to the god Fharlanghn, whom he's taken to worshipping. Getting to play out his gradual development and growing understanding of other creatures and himself has been great fun (he just learned what fear means when he ran into a rust monster

).
Kylian Davandi - Gnome beguiler. Currently being played in a Shackled City AP campaign (PbP). Incredibly smart and completely amoral little so-and-so. The only reason he's not actually evil is that it takes too much hard work and people tend to try and kill you. He functions as the brains of the party and is at his best in a fight shouting tactical orders to others while simultaneously boosting their abilities and weakening others. Constantly manipulates NPCs with a combination of diplomacy and utter bull.
Cedric Marne - Human rogue/duskblade/crusader. Currently being played in a homebrew campaign run by Rolzup from ENWorld. See my sig for the world's worst paladin. It's much the same concept, with some cosmetic differences (and he hasn't actually got levels in the paladin class).
Meiji Kitsume - Human shugenja (modified). Currently being played in Mallus' incredibly idiosyncratic CITY campaign. He's a duplicitous, lying, cheating, whoring, cowardly SOB. 'Nuff said.