There are new Zune HD applications in the Zune Marketplace, some of which take advantage of the 3D features that came with the last firmware update.
Vans SK8: Pool Service - 3D game in which you tilt the Zune to control a person on a skateboard that is skating around pools.
Piano - Exactly what it sounds like. A piano using the multitouch screen. You can see up to one octave of keys at a time.
PGR: Ferrari Edition - A racing game. Pretty straight forward. Use the mutitouch controls and tilt the zoom to control your Ferrari in a 4 car race.
Audio Surf - Simple, but fun. In this 3D game you tilt the zune to steer a vehicle to avoid options and pickedup colored squares for points.