While Blizzard is primarily known as the developer of Warcraft and Starcraft titles today, I have a deep affection for the games produced in the company's early years. Today, I'm a pretty happy camper, as one of those classic titles has been released for free on Blizzard's Battle.net service, Blackthorne.
A weird mix of fantasy and science-fiction, Blackthorne is a 2D platforming game where the deposed prince of an alien planet, hidden on Earth at childhood twenty years prior, returns to his world to save it from the despotic monster who now rules. It's a bit like the original Prince of Persia with a sawed-off shotgun in gameplay.
You can try Blackthorne out yourself starting today by going to your Battle.net account and acquiring it from the client downloader.