Hero Core is a superb 2D shooter by Daniel Remar (best known for making Iji). You control Flip Hero in his quest to destroy the machine warlord Cruiser Tetron once and for all. While it is possible to fight Tetron very early in the game, you can also choose to explore the game world (in a manner reminiscent of the Metroid games) to upgrade your weapons and defences. The game features simple but effective 1-bit graphics, a cool retro soundtrack and some well-designed game mechanics and bosses. Expect a lot of intense bullet dodging and button mashing (an autofire option is available, however).
Screenshots, video and download link here. (Windows only)