Fantasy Flight Games, 2000, 2-6 players, no age specified but I'm assuming ages 12 and up. In Twilight Imperium players control different alien races in a race for galactic domination. By taking control of planets, players amass the resources necessary to build up space fleets (used to further expand their empire) and influence at the galactic council. Resources can also be used to increase your empire's level of technology. Players may form trade agreements amongst each other that can be broken and re-made whenever the political winds change. This is a pretty good game although it does have the feel of being cobbled together from other popular games. I think it most closely resembles Warrior Knights (political conferences, etc), Civilization (its system of acquiring technology and its victory track), and Axis & Allies (the way the space armadas function).
The rules are pretty long, so expect to spend a good 20-30 minutes going through them before getting started. They're pretty well organized, but we found them to lack needed specificity when it came to answering some of the questions we had (we wound up making up a lot of in-house rulings to cover grey areas, something I'm not real fond of doing). Games themselves take a good long time. Our first game took around 8 hours to complete, and I'm sure subsequent playings will still be in the 5-6 hour range, depending on the number of players. I like the fact that victory is achieved by advancing along a track made up of individual goals (rather than the typical eliminate-your-enemies-one-at-a-time method employed by most war games). Twilight Imperium makes use of the now popular moveable hex style of building the board, so each game will play a little differently. The pieces are nice looking and sturdy, but set aside time before you start playing to cut them off the sprues - it is a long and tedious process. Although we were a little concerned that perhaps the pieces were a little too large to comfortably cram onto the planet hexes, it didn't really become a problem for us.
My copy is a "second edition", although I have no idea how it might differ from the first edition. Overall this is a decent game with a lot of promise, but it does have its problems. I really dislike the method they've devised for cobbling together the board. First, the central system of the game (Mecatol Rex) is placed in the center of the playing area. Then each player places their homesystem a distance away from the center, approximating its ultimate position. Then players are dealt out random hex tiles and take turns placing them, starting from the center and working out. The problem with this system is that you're pretty much doomed (or blessed) right from the get-go, based on what tiles you are dealt. In a recent game I was dealt a half-dozen super powerful systems which I naturally placed strategically close to my home system. And so it was no surprise that I eventually won the game. Also, allowing players to concentrate desireable systems next to their own home systems tends to cause the game to bog down in stalemate; players concentrate on their own little corners of the universe and don't really venture out to foment conflict with other players until the game is nearly over. I think a better system would be to simply randomly place all the board tiles and then let players choose where they want to place their home systems. This would more closely approximate how Warrior Knights works and make for a more balanced game.
Update: In 2005, Fantasy Flight Games released a 3rd edition of Twilight Imperium that completely wrecked this otherwise entertaining game. Yes, the game pieces have been much improved, but layers and layers of needless complication have been added to the game, turning even the simplest of tasks into a byzantine maze of complexity. We spent close to an hour trying to decipher the new (thick) rules before giving up in frustration (deciding that if we were ever going to play this game at all someone would have to sit down and read through the rules beforehand and then just explain them to everyone else). I won't bore you with the details, but I will advise you to hang on to your 2nd edition copies of TI like grim death. They're going to skyrocket in value. Buy 3rd edition for the pieces if you must, but attempt to play it only at your own risk.