You remember Daikatana? The game that was supposed to show Half Life how first person shooters should be done? Unfortunately, due to the various issues during its production cycle, the game is remembered as one of the biggest commercial flops in video-game history.
However, not everyone hated Daikatana, it seems. There are still groups of people out there who enjoy playing John Romero's biggest regret. And thanks to these people, Daikatana is actually much better than you might remember it.
If you download the homebrew Daikatana 1.3 patch, you get all kinds of cool features, including HD texture support, glowmap support, multiplayer through QTracker, plus a plethora of bug fixes. What's even more important, though, is that you can FINALLY turn off your sidekicks and play the campaign without them (despite the people working on the patch not recommending it), or make them invincible. In other words, Daikatana is now both playable and enjoyable!
So if you're interested, you can get Daikatana on Steam. Once you do that, don't forget to download said 1.3 patch. Finally, make sure you join the Daikatana Multiplayer Association if you're in the mood for some multiplayer fun - a small fan base is keeping the action alive all the time.