Joining the ranks of the modern retro-style shooters we've been seeing so many of lately — a great trend, I might add — is Wrack, the colourful, arcade-esque FPS for PC that's been under development for six years.
Wrack is singleplayer-only, and it promises "unlimited content" through user-made maps and mods on the Steam Workshop (though of course, the game has its own campaign). The arcadey aspect comes from the game's scoring system, which rewards skillful shots and kills.
Overall speed and gameplay is very much reminiscent of Doom, but with Mega Man-style minibosses and bosses. That, combined with a somewhat Borderlands-like aesthetic, results in a game that looks like this:
If you wanna take a look or read some user reviews, you can check out the game's Steam page here.