Which missing TCS topics on Wikipedia would you most like there to be an article about?
They could be glaring omissions or just topics you think should really have an article.
One topic per answer please so that the most wanted ones can be voted up.
Update 5/2/2017: Shuchi Chawla is leading an effort to improve TCS coverage on wikipedia. I'm adding this update in the hopes that people will update their answers as appropriate, add more answers, and/or contribute to the effort!