Your champion would be soundly trounced by the more sophisticated strategies I described. Since even sword and shield is fairly simple to implement and plenty effecient enough to run in idel, just a bit of coding could bring your Roshambo competition from amateur to world-class.
thraxil: Roshambo and Prisoner's Dilemma have distinctly different flavors because Roshambo is a zero-sum game, in which no cooperative strategies are possible. Tit-for-tat is now getting practical application in the choking algorithms for my project BitTorrent, which are very analagous.
isenguard: That paper is interesting, but I'm very leery of empirical measurements of constraint satisfaction heuristics which don't set the actual record. Experimenting with 10 when the record is 21 is pretty bad (it's even more now). There is only one fair measure of time, and that's minutes and seconds.
If we mark the minimum number of moves it takes for a knight to get from the origin to each square on an infinite chessboard, we find there are four local maxima - exactly two squares away from the origin along each of the four diagonals. Generalizing to knights which move x in one direction then y at a right angle, with x and y relatively prime (the standard knight has x = 2 and y = 1) it appears that there are always four local maxima, and they're always on the diagonals. I don't know why this is.