I've spent most of the evening playing Spelunky on PC. It's a fusion of ZX Spectrum classic Fred and a Roguelike. The aim is to try and pilfer as much treasure as you can, while making progress though the subterranean levels.
It's full of neat touches - I picked up a golden idol, which resulted in the ground shaking before a huge boulder chased after me in an Indiana Jones style. Unlike Indy, however, I didn't survive.
You have access to ropes and bombs to help you through the mines, while shops are scattered throughout the levels selling extra bombs and weapons.
In typical Roguelike style, there are many fun ways to die, and as the levels are randomly generated, you never have the same game twice.
It's free to play and can be downloaded from here
It's also coming out on Xbox Live Arcade in the future.