Check out the fun article on AV Club. I always disliked Scrappy Doo as a kid, but never quite realized why. Of course, this list includes a few I'm not very familiar with, and omits a few that I would definitely include:
- "Lil" the crazy lady in the Boy Scout uniform on Survivor: Pearl Islands
- Uni the unicorn on the classic Dungeons & Dragons cartoon (soon to be released on DVD, by the way!).
- Dr. Gaius Baltar on the modern Battlestar Galactica, a character horribly out of sync with the rest of the show.
- Ana-Lucia Cortez on Lost, for reasons that should be obvious to most who watched the show. Partially for a poorly written, poorly realized character and partially for Michelle Rodriguez's two-expression performances.
- Dr. Pulaski from Star Trek: The Next Generation.
- Rosalind Shays on L.A. Law (man, that actress had kind of specialized talent!).