In addition to his great contributions to EECS, Elwyn Berlekamp is also a leader in the field of Combinatorial Game Theory. In writing the 1984 book Winning Ways for your Mathematical Plays, Berlekamp, John Conway, and Richard Guy created Combinatorial Game Theory. CGS is much more advanced and intricate than "regular" (i.e. John von Neumann's) Game Theory; it covers games of no chance of complexity from Nim to Go. In fact Mathematical Go is another of Berlekamp's specialties and currently simple games can be solved mathematically (sometimes in analysis of tournament games catching errors played). Volume 3 of WW is soon to be released.
Trivia: Berlekamp is the only Mathematics professor at UC Berkeley to not have degrees in math (but rather in EECS).
(I had the fortune to take a graduate course in CGS by Berlekamp in 2002. Half the fun was in listening to Berlekamp's anecdotes about the insistence of his English colleagues of alliterating terms, meeting famous Go players, one-upping people by naming a composed problem "4G4G4G4G4" (Four Games for Gardner for Gathering For Gardner Four - http://www.msri.org/publications/books/ Book42/files/be4g4g.pdf).)