This was posted on Siliconera as of 5/23/2013:
The PC version of Tomb Raider is on sale on Green Man Gaming. For the next 22 hours, you can buy a Steam key for the game for 66% off—that was about $17 for me, although prices vary by region.
Additionally, you can use the following code to bring the price down even further: GMG20-LLASD-D8WBQ. After applying the code, I managed to pick the game up for $13.60.
There’s no telling when the code will expire, so you probably want to act quickly.
This is my first EVER PC game. I've been waiting for Tomb Raider to go down in price, regardless of system, and with my new gaming laptop coming in next week, I figured this was the perfect opportunity.