If you buy it from GreenManGaming gaming you get Bioshock Infinite, $15 GMG credit, Bioshock 1, XCOM Enemy Unknown, the Industrial Revolution Pack and your choice of either Civilization 5, Spec Ops The Line, Mafia 2, Bioshock 2, or The Darkness 2.
If you buy it from Amazon you get Bioshock Infinite, $30 credit towards 2K Game downloads on Amazon, XCOM Enemy Unknown, the Industrial Revolution Pack and Bioshock Infinite: Mind in Revolt, which is a 30 page book of some kind that has some back story on the sky-city Columbia.
If you buy it from Steam you get Bioshock Infinite, Bioshock 1, XCOM Enemy Unknown, the Industrial Revolution Pack, and seven Team Fortress 2 items.
The GreenManGaming version has the most bang for your buck, but I already own all of those games. The Steam version will get you a whole mess of TF2 stuff if you're into that. I went with the Amazon copy, hoping something good comes out of 2K Games in the next year.