Biozone is a 2D side-scrolling STG type of small indie game published by KONAMI in 2010. It came with old-school retro graphics, exciting background music, and flexible character actions design. I believe players who like exciting will fall in love with this game, even if many years later.
Intrusion 2 is a 2D shooting game developed by the independent producer Abramenko Aleksey, it has the similar style with "Metal Slug Series". The game blends the classic 2D gameplay and style, is a platform action game, with many physical elements, and supports PC and Mac platforms at the same time.