Kriegspiel is the name given by a French designer to his game looks like sort a sort of a cross between Chess and an Avalon Hill style wargame. It was mass produced in 1987, and now is out in a computerized version. There’s no AI, though, so you’ll have to find an opponent. It looks interesting. There are both Mac and Windows versions.
Urban Dead is a free MMORPG where you play the survivor of a zombie outbreak. It’s got a huge following among gamers of all kinds.