Hot Hardware reports hearing about the promotion directly from Nvidia and says the offer is part of the launch celebrations for 2K's Mafia II, which was launched on August 24 in North America, August 26 in Australia and August 27 in Europe.
"We here at NVIDIA are super excited about the incredible experience that can be realized when playing on a GeForce GPU. …To celebrate the launch of Mafia II and the gaming goodness it provides to GeForce owners, NVIDIA is offering a coupon code good for one FREE digital download of the complete PC version of Mafia II with the purchase of any qualifying NVIDIA GeForce GTX 465 and above."
The offer is only available while stocks last, so if you've been holding out on purchasing a GeForce and the offer of Mafia II for free has pushed you over the edge, you'll want to get in on this deal quickly.
Source: Hot Hardware