Alien Swarm! What was once an extremely popular UT2k4 mod has not been revamped with the Source engine and is not being released today, July 19th, for FREE on Steam!
I'm downloading it right now. I see a bunch of you already have, but I thought I'd still spread the word.
Feel free to post your impressions! I'll be coming back here in an hour or two saying what I think of it
EDIT: Played with some friends for a few hours. Feels very much like a top-down L4D, which is a good thing. There are loads of weapon and load out, options. You choose from one of four classes, essentially Tank, DPS, Tech, and Healer. You then choose your main weapon and your secondary weapon, along with some sort of utility (damage amp, armor, freeze grenades, etc). The game is also quite pretty. The lighting is very atmospheric and the monsters are all detailed (to the point where you can easily tell which type you're fighting).
I'm headed to the gym so I'll give a more detailed review later, but my only main criticism right now is that the servers are being absolutely assaulted. The lag is pretty bad.