Duke Nukem 3D 1.0

This game has a long list of cool things that haven't been attempted in 3D action games, yet. The weapons, for example, kick-butt:
There's a mine that can be placed on any wall and sends out a laser trip beam-- perfect for multiplayer games.
There's also a shrinker ray that reduces an opponent to the size of a G.I. Joe, at which point they are foot fodder--watch them splat!
As in Shadow Warrior, you can swim under water, and even shoot players who are standing outside the water, or vice versa.