Alone in the Dark, when it came out, was one of those games that others attempted, and typically failed to emulate. An early survival horror game that combined Lovecraftian horror with action. The pacing, and style of the original game are nothing short of fantastic. It may take you a moment to get into the swing of the controls but it's worth it. Unfortunately, the later games in the series never quite measured up to the first, but it's worth buying just to play the first in the series.
Really not sure why Daikatana would be on this site other than as a monument of infamous gaming history. Daikatana has become synonymous with everything that was wrong with game development in the 90s. Over the top, Xtreme attitude marketing, endless delays, and in the end, an FPS that is brown, ugly and boring. That's the problem with Daikatana, it's a bad game, but not bad enough to be hilariously bad like Big Rigs: Off Road Trucking. It's just a frustrating mess with terrible weapons and embarrassing companion AI. Also, the black character is named Superfly Johnson? Why not just call him Stepin Fetchit and be done with it?
I really enjoy DEFCON, and have even used it as a teaching tool about nuclear war. Presentation-wise it's one of the most unique games out there. No fancy models, no cpu chugging physics engine, just a wire-frame map of the world with figures moving about. Nonetheless, as you get closer to zero hour and the eventual launch of your ICBMs the game gets increasingly tense, and dramatic. Finally, as your cities disappear and the death toll mounts, the horror begins to hit home in a surprisingly personal way, helped along by a brilliant ambient score. The crowning touch is knowing that the bunker-buster is heading for your bunker, and watching as the counter ticks down to your certain death. The game has a bit of a learning curve and you'll likely lose badly the first few times you play it, but once you master the basics, you'll find this can be a fun way to spend an hour.