Furious Angels [Steam store page]
Simple yet elegant gameplay. This is a great example of how to make a game engaging but super accessible.

Beat Hazard [Steam store page]
An interesting mix of music and gaming - enemies generated by songs. Disappointing that they charge extra for multiplayer (DLC - BH Ultra).

The controls on this underwater side-scroller are decent, though I wish there was a way to bind songs to a hotkey. A way to quick-save instead of save points within the game would be nice as well.