So apparently Insurgency 2 survived the failed Kickstarter, and hoo-fucking-rah for that!
As a gift to the Kickstarter community they've handed down this code:
Which will give you 50% off, making it a 10 dollar game, at http://www.playinsurgency.com/
I haven't tested it, so I don't know if it's a one-off.
Insurgency was originally a source mod, which focused on extremely difficult squadbased gameplay.
One shot could very well kill you, so you could say it was a very punishing Counter-Strike. Definitely not for everyone, but I thought it was awesome.