UltimateUnknown on 12 June 2012
Blacklight Retribution, a very recently released free to play FPS with very good graphics and mechanics. It does have somewhat high recommended system requirements for FTP games that I have seen, but with your nvidia GPU and quad core I7 you should easily be able to run this at full glory at 60 FPS. Highly recommend this.
I am not too big into mmos, but a good free one (without subscription fees) is Rusty hearts. I had quite a bit of fun with the addictive combat system. You can download this one through steam for free.
