WAR! Politics, bloodshed, heroism, betrayal, religion, luck, and pure cussed skill: there are very few topics that capture the human heart like war. So, of course, there are games about it. Make sure to look at So You Want To Write A Story for good general advice, and it might be a good idea to check out the other gaming genres on So You Want To for other ideas as well. (Much of this is being reproduced and inspired by the Write An RPG article.)