If for some reason you haven't picked up any of the BioShock games yet but have been really wanting to, now's as good of a chance as any to change that. This weekend on Steam you can get all three games (minus the DLC) for $14.99. Not $14.99 each, $14.99 TOTAL! The BioShock games are arguably some of the best games of its genre to come out in the past decade and definitely worth checking out, and now is a great opportunity to do so. This sale goes through May 12th so you still have some time to consider it.
As for the individual games (in case you already own at least one of them), BioShock 1 and 2 are on sale for $6.59 each while BioShock Infinite is on sale for $9.89.