If you haven't heard of this game yet: http://www.youtube.com/watch?v=4HfCqw_8iKo
Warning: this game is rather graphic and drops a lot of vulgarities. I'm not a huge fan of overly violent video games, but a deal is a deal and this game certainly looks fun to me.
Free shipping is only for Amazon Prime members. PC version is available, but no $20 credit available.