TYRIAN 2000 / Epic Megagames / PC
Tyrian was an excellent space shooter put out by Epic MegaGames back in 1995. In 1999, it was re-released as Tyrian 2000, with a new mission and some bonus features added. In 2004, all versions of the game were released as freeware by the original designers.
While the formula is essentially the same, Tyrian 2K has it over most conventional space shooters in a number of ways. It can be played solo or with another player (hot seat, or via a modem connection). In two player mode, players have the option to join together into a super-ship whose steering is controlled by one player, and rotating turret gunfire controlled by another. Single players also have a detailed "story mode", which connects the levels together through an ongoing narrative, and offers the option to buy ship upgrades in between levels.
The graphics are colorful, the music is some really good synth-rock stuff, and the bad guys of the game are an evil space megacorporation named Microsol. What's not to love? If you at all enjoy shooters, be sure to give this one a look.