Here’s a nice promo from Green Man Gaming. Pre-purchase BioShock Infinite now and you will get the original BioShock game and XCOM: Enemy Unknown, plus one of the following games free: Spec Ops The Line, Civilization V, Bioshock 2, Mafia 2, Darkness II.
This is probably by far the best deal out there now. 60$ for US ~46€, 37,49€ for EU, 23,99GBP for UK ~28€. For this you’ll get BioShock Infinite + XCOM + BioShock 1 + game of choice from the list there.
It’s Steam redeemable.