Wolfenstein Enemy Territory (more known as just "ET") is a FPS game, just like Halo. (except it's free :P )
First released in 2003, it is one of the best FPS games ever released imo.
Here's one of my best scores from awhile back:
This was on a mod called NoQuarter.
There are quite a few mods in ET.
I'll name the popular ones.
Jaymod (More like gaymod, hitboxes are terrible :P)
Nitmod (The best, I love it <3)
NoQuarter (new weapons, new skills, new everything!)
Silent (one new weapon + new hitboxes ofc)
TJMod (To TJ with, duh)
ETJump (Another TJ mod)
Jaymod is what most of the popular servers use, such as some of TWC's servers.
Nitmod is what my server uses (Beginners), and is the hardest to play on of them all. Small hitboxes.
NoQuarter is fun for pretty much anyone.
Silent is a nice mod with really nice hitboxes and tripmines.
TJmod: never tried it, never will.
ETJump is a mod trickjumpers use to well.... jump!
PS: If this is in the wrong section, my bad. Move it to where you think it belongs.