Borderlands. It's an upcoming FPSRPG by Gearbox Software, developers of the Brothers in Arms franchise, that's looking to be absolutely amazing. They're boasting over 650,000 UNIQUE guns alone (several orders of magnitude over every gun found in every game on the Xbox360/PS3 combined), with thousands of variations e.g. different scopes, blades, etc. on the gun, within each unique weapon. Over 500,000 unique pieces of armor so far, and over 10,000 unique vehicle parts ranging from chain guns to rail guns to rocket launchers (more parts than the most in-depth racing simulators out there). From what we've been told so far, it's an amalgam of the Diablo series, Mad Max (awesome movie, watch now) and Halo, with a hint of a Firefly vibe.
It also features drop-in-drop-out 4 player online co-op with persistent characters, and hundreds of other things that I could go on about for a while, but I think it'd have the best effect on you all if you were to research the game yourself.
Spread the word, as this game has little to zero hype and definitely doesn't deserve that.
Here's a few links from a year or so ago about the game. Enjoy.
http://www.gearboxity.com/content/view/407/36/ [http://www.gearboxity.com/content/view/407/36/]