Crimson Fields is a rare breed of game indeed. It's turn-based, hex-based, freeware and released for the Pocket PC. What's more, it features 3 multiplayer modes (including play-by-email), fully supports single-player gaming, offers complete map & campaign editing tools and even has a passable plot. Grab yourselves a copy here.
Related posts: Oric Atmos on the PPC, Machines at War, Warring States Pocket PC, Sky Force