The classic Another World is available on Steam 75% off. If you’ve never played it, I definitely recommend checking it out, it’s a classic that has inspired game developers everywhere. Another World is definitely proof that even development teams consisiting of only one person can accomplish incredible things. Eric Chahi did an excellent post mortem at GDC which is available on video for free at the GDC vault: http://www.gdcvault.com/play/1014630/Classic-Game-Postmortem-OUT-OF
Fez, which I recommended as one of my top 5 games of last year, is also available at 50% off!