What is your favorite character that you have NOT played?
Put simply: A Goliath rogue.
D&D Wiki calls them: "massive creatures unafraid of throwing their weight around in a fight. Highly competitive, these strong nomads can prove to be powerful allies and welcome additions to any adventuring party." They were a lot more than that, however. Their favored class was barbarians; they live in the mountains, have bluish-grey skin, and hard nodules randomly on their bodies. Picture giants, but of Medium size. Rather, they're Medium size, but so massive that you treat them in many respects as a Large character.
OK, you have that picture in your head?
Now make him a rogue. Blow up his Move Silently and Hide skills (a.k.a. Stealth). Maybe add in a Cloak of Elvenkind. Make him ultra quiet, ultra sneaky, and ultra...well, ultra rogue. But when you look at him, he's this big lumbering mass of flesh. It's a great contradiction. I want to play one just for the shock value, and I've been waiting for the right time to spring one on my group.
Until about 6 months ago. One of our other players--who does not like playing the same race twice--was looking for an innovative character idea. So I gave him this one, thinking he would never try it.
Well, he did. And he died within one session to the attack of three giant spiders. A very ignominious end. There was a lot of mocking and laughing. So I've shelved the idea.