So many I've loved... I'll list my top 3!
Name:Vincent Fabalis
Race: Human
Class: Fighter
Backstory: A simple farmboy out exploring the world, ever naive of the the world, always retaining his boyish innocence.
Campaign: Forgotten Realms
Edition: 3/5
Plot: He was a simple farmboy who wielded a zweihander custom made for him by the first dwarf he ever met: the town blacksmith (in our campaign, Featherdale was a tiny little village) Hammerfist, who actually had an enchanted hammer for a hand. He's traveling the world with an Incarnum user, after having protected him from some suspicious and uppity townfolk. " Come on, pa! This guy helped the baby out! He din't do it! Honest!" He's a rather plump boy, prone to hour long meals, loving anything blueberry flavored, and no matter what, the best praise he can EVER give any food is "It's almost as good as my mom's!" Even if it was the god of cooking himself, it'll never be as good as his mom's. He loves his mom.
Name:Thamior Nailo
Race: Everything
Class: Sorcerer/Binder
Backstory: An insane sorcerer who sold his soul, got it back, and has died and been reincarnated numerous times.
Campaign: Forgotten Realms
Edition: 3.5
Plot: Thamior was a young, naive Elven sorcerer who was rather insane, but not dangerously so. After his tree-top village was destroyed, he traveled with a leftover soldier from the invading force: a half-ogre/half Red Dragon named Krusk Femur. After both sold their souls for incredible equipment, they lived happy lives adventuring, and getting repeatedly high from constantly licking his Toad familiar, Toadie. He spent much time in prison and crying his heart out when separated from his toad familiar for any point and time. Having once died and been reincarnated as a goblin, Thamior was determined to be an elf again. So he has Krusk kill him many times, while making a local Druid cast Reincarnation on him over and over again until he was finally an elf (yes, his CON is currently around 4) Currently living with a constantly drunken Krusk, a rather abusive shadowcaster roommate named Smoke, and making a living as Waterdeep's very own version of Dr. Seuss, writing wonderful, drug-influenced children's tales under the series title "The Adventures of Toadie". Toadie is a great warrior who travels around constantly foiling the plots of Corpsey McGee (a thinly veiled stab at the person he originally sold his soul to, whom Thamior doesn't much care for. His name was Carkus)
Name: Gax Foulfart
Race: Goblin
Class: Fighter
Backstory: A goblin too smart for his tribe (INT and Wis of 10 each) with a very mean and bloodthirsty bend.
Campaign: Forgotten Realms
Edition: 3.5
Plot: Gax has vowed to get revenge on his clan. He was kicked out by the chief for being too smart, but knew he, by himself, wasn't strong enough to take out the guards and himself. He travels by himself, fighting wherever he can, trying to deal with his racial predisposition of cowardice. Among his travels, he attacked an Elven wizard, who layed the following curse upon him: Whenever his surname is spoken, the player must roll 1d20. On a roll a 1, the character who said it will poo his pants. On a roll of 20, the character will stink out the room. A regular fart occurs on any other result. Gax took the curse as a blessing, and continued on his ways after the freaked out wizard teleported away. Gax has the habit, which he oh so enjoys, of frequently crying out his full name at any given time, enjoying his own stench, and loving the ability to create it at will. He carries with him a goblin-sized Buster Sword, and hopes to one day be strong enough to kill his clan. (He's currently 26, but doesn't realize just how strong he's become)