terrible lag..

turtLe

I get teeerrrible lag when I try to play, way more than 100 ping would get. I guess its me, because if everyone got this there wouldn't be this much people playing. Any ideas?

Basically, if there are any more than 3 people shooting at me people skip about 5 feet. Projectiles come out very delayed, also

kamishizuka

It could be your graphics, I think, or also your connection. Usually I don't see any stuttering unless practically the entire server of players is in my view (which is usually 40+).
Graphics stands out to me then, if you're having stuttering issues at 3+ players on screen. I'd check graphics settings, maybe find the HUD that gives you a FPS counter (unless someone can tell me a console code to do the same), and see if that's part of it.

Turkeh

You can display your FPS (in a quick 'n dirty fasion) with the console command

show("$FPS::Real");

That will place a small white box in the upper left corner of your screen, with your FPS.

You can disable by issuing

show();

in the console.

Another possibility might be CPU Affinity, if you have a multi-core/cpu machine.
You can find some methods to deal with that here.