What are good topics for literature review prizes?

The last prize, for the best literature review of spaced repetition, was moderately successful, inspiring a pretty good review of the academic literature on spaced repetition. I am interested in experimenting more with prizes, but I would like to get input other people’s input: what are other good topics for future prizes?

The topic should be:

  1. Well defined.

  2. Not too big. Something someone could understand pretty well in two weeks.

  3. Academically researched.

  4. Relevant to being effective.

I am also open to projects besides literature reviews but literature reviews seem the most attractive to me right now.