[Hugh Manatee]

If you have about $50 to drop($30 for the GBA, $10-$20 for the game), get a classic gameboy advance(the non flip top Version), and Advance Wars 1 or 2, they are excelent war strategy games you can take with you where ever you go. It's kinda like Empire Deluxe, but each unit is set up to "rock, paper, scissors" another unit. Navy is a little underpowered, and air is a little overpowered but it's still fun. You also get to chose from about 16 different Commanding Officers which define your army's traits. Also there are many "tactics" games for GBA, like Fire Emblem, it's like Advance wars but with RPG characers instead a modern army, also Tactics Ogre: Knihgt of Lodis, one of my Favorites, you raise an army of 32 charachers, customize their classes, spells, skills, and armor, and go on an adventure to retrieve a powerful artifact. It has excelent multiplayer if you can find someone else who has it. I haven't played them yet, but Final Fantasy Tactics and Onimusha Tactics are similar to Tactics Ogre. There are also lots of RPG adventure games out for GBA too.

I second Stars! It's a little primative but excelent.

Alpha Centauri and it's expansion are VERY good, too.