Mercenary Kings offers local or online co-op for up to four players.

This game features an incredibly deep and varied weapon customization system, allowing players to customize their experience.

This game features a good weapon customization system. The only downside is that this can lead to a certain level of grindiness – but not too much.

Mercenary Kings is the spiritual successor to the Metal Slug games: It's a two-dimensional, pixel art, side-scrolling action shooter with co-op multiplayer.

If you don’t know Paul Robertson, check him out. From Adult Swim animations and dozens of video games to feature films such as Scott Pilgrim vs. the World, Robertson has built an impressive portfolio of great pixel art and animations.