Hangin' at the Hulk

Allow me to recommend a game. There is a board/miniatures game called Space Hulk, and a free open-source implementation for Windows. It's great - simple, atmospheric, well-balanced, hard-to-win, and unforgiving of mistakes. In the boardgame the Marine player has a 30-second time limit for his moves - I don't suggest this if you want to retain your sanity.