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!
Some missing topics from my collection of graph algorithms articles:
Also, not so much missing topics, but a lot of the articles on topics covered by undergraduate algorithms classes kind of look like they were written by students in those classes. There's a deeper level of understanding missing, and they take a dogmatic point of view that reflects a single textbook rather than a synthesis of multiple sources. More expert help there could be useful.
I would love a Wikipedia page on the Abstract Tile Assembly Model.
The entry on the Johnson-Lindenstrauss Lemma lacks a complete set of references, and might also benefit from a high level explanation of the different types of algorithms available.
The current article on computational topology covers only one small (but important!) subfield. Other subfields are covered in topological data analysis, topological graph theory, discrete exterior calculus, and possibly even topological quantum computing. But even combined, the resulting article would be incomplete.
Yes, yes, I know.