Old, fun FPS

[MeatshieldDeluxe]

Deus Ex
Doom
Doom II
Battlezone {It's a FPS/RTS hybrid}
Marathon {It's a MAC game but you can find a ROM for the PC}
Marathon 2 Durandal
System Shock
System Shock 2
Duke Nukem 3D
Shogo
Rise of the Triads
Star Wars Dark Forces
Star Wars Jedi Knight Dark Forces II
Catacomb 3D
Wolfenstein 3D
Hovertank 3D
Blood
Quake
Quake II
Quake III
Half-Life
Half-Life Opposing Forces
Descent
Descent II
Descent 3
No One Lives Forever

What? No Serious Sam???

 

[Daveman]

Timesplitters (2 for preference, but the original was awesome too) was the funniest FPS ever. And now it can be defined as old school. Definitely pick that one up.

Wonderful wonderful stuff it is.

 

[Gestapo Hunter]

Unreal Tournament

 

[shadow_pirate22]

You might enjoy Jedi Academy. It can be a TPS or an FPS, and you get neat powers and a lightsaber and such.
It also came out years ago, so your computer should be able to run it pretty well.

I thought I was the only left who liked Jedi Academy. Good to know I'm not alone.

You are not alone at all, brother.

 

[Doc Theta Sigma]

You could try Painkiller. From what I've heard its so good you'd step over your own mother to play it.

 

[Shadefyre]

Postal and Postal 2 anyone? Or would those be too recent?