The newest free game as part of Xbox LIVE's 'Games with Gold' promotion comes with a buddy; not only is Dead Rising 2 free for the next two weeks, the XBLA prequel, Case Zero, is also free. Are these games super new? No, but they're good and, costing you nothing, there's no reason to skip picking up both games. I'm still waiting for a free game that blows me away or peaks my interest at all, but, being who I am and owning as many games as I do, I doubt that will ever happen; however, I'm in the minority and I hope these free games (and future free games) do more for you than they do for me.
Dead Rising 2 [GoD] - ($29.99 ---> FREE)
Dead Rising 2: Case Zero [XBLA] - (400 MS points ---> FREE)
And remember, the Xbox LIVE 'Games with Gold' promotion is only open to Gold members (thus the name), so if you're rocking a Silver (Free) account, you're shit out of luck.