Gang Garrison 2

Gang Garrison 2 is a so-called retro demake, a cool concept where a modern game is converted to a more retro-like style. In the case of Gang Garrison 2, it has taken inspiration from Team Fortress 2 and turned it into a 2D 8-bit styled game. It's not only an impressive feat to do that, but Gang Garrison 2 is also surprisingly complete, containing 9 different classes and team-based multiplayer on several different maps. Give it a go, or check out the source.

It wouldn't run on a NES, but the retro-feeling sure is there.