This is an odd one, so how about the character I never got to play past two sessions?
Going back to Hackmaster again (which I consider an AD&D edition--3E that should have been!), the GM had set up a Hommlet campaign--well sort of--using the hacked version of T1, The Temple of Existential Evil with the twist that party was on the Neutral-Evil Axis rather than the Good-Neutral one. Now, no one else in the group had previously played T1 in any form (I have about 10 years on the rest of CLD). The DM had no problems because, as a fellow DM, he knows that I would never use knowledge of treasure and what's out there to my advantage. I generally hang back on that knowledge and stay out of "party decisions." And, besides, the hacked modules usually mix things up anyway.
Well, I decided to play a cavalier of Hextor, tasked with stopping the rise of Chaotic Evil in the area around Hommlet. Oh, did I have plans! I was going to help train the militia, try to do some conversions on the side, and stop Chaos, all in the name of the Herald of Hell! I knew what I looked like (dark and handsome, like Rufus Sewell in A Knight's Tale!), had my weapons of choice picked out for levelling, pre-thought conversations of how to do with pesky do-gooders questioning my motives, everything!
Unfortunately, we only played two sessions. One of the (now former) members of CLD decided to play Stupid Evil and was screwing up the game purposefully for the rest of us. At the same time, he was trying to break the DM's game. Not cool. So, Sir Demetrios never realized his full potential.
Until tomorrow, gentle readers, think of what might have been!