Half-Life
Up StarCraft Half-Life Diablo Dark Reign Quake StarCraft Campaign Map Editor

 

Voted the best 3D action game of 1998 at E3. Claimed as game of the year by all major computer and games magazine. Half-Life is undisputedly the best 3D action game I have ever played. What makes it special is the AI of the computer; computer enemies are intelligent in that they will run away when being shot at, they can hear your foot steps, and they can even attack each other.

I have completed the original Half-Life game and the HL demo "Unlink", both of which is a lot of fun to play and very satisfying when finished. I have yet to play the Half-Life Team Fortress add-on, which is specifically designed for multiplayer team games on the internet and LAN.

You really need a 3D accelerator video card though, otherwise the game is very slow, but then that goes for all the new 3D games which are designed for high end computers.