Spider O'Malley
This is probably the most colorful character I have ever had that only lasted two sessions. Actually, qualifications aside this guy might be the most colorful. The campaign was a Sabbat chronicle and he was a Brujah antitribue. He was inspired by this outrageous dude I saw walking around the mall when I worked there, but I took this a little further.
The look: He was bald, with a tattoo of a spider web on his head. He wore a derby hat and had a giant handlebar mustache. His jacket was a navy peacoat with the sleeves torn off. His right arm had a navy seals tattoo and he wore a $20,000 rolex watch. He had a stained wifebeater shirt and torn jeans, with combat boots on his feet. Usually he carried a silver tipped cane.
Mannerisms: He interrupted a lot. His attitude was defiant but he understood when he had to do what he was told. He liked to chew Mars bars and spit them out.
He had near total amnesia, but during the game he found that he had been sired because he had tormented his sire in life and that guy hoped he wouldnt survive the initiation ritual. That idea backfired in a big way.
For those of you who dont know about Sabbat initiation rituals, the one that he was subjected to was pretty standard. A group of 5 of them were taken out into the desert and told to dig a giant hole. Then the Sabbat drains them all of blood (sending them into frenzy) and throws them into the hold and buries them. Whichever one survives gets to become a Sabbat. During the digging his sire mocked him, so he hit him with a shovel and knocked him into the hole. The other Sabbat thought it was so funny that they forbade him from attacking Spider. This only fueled the resentment between them.
Needless to say he, along with one other, made it out.