On the one hand, Kingpin is an unusual approach to the FPS that takes place in a bizarre and intriguing anachronistic setting, features the most distinct character design this side of Team Fortress 2, surprisingly good voicework, and maintains a grimy, very memorable atmosphere throughout.
On the other hand, Kingpin is a sloppy and at times transparently half-assed game that never delivers on its promise and eventually descends into an unstructured shooting gallery, one marked by silly boss fights, outrageous difficulty, and enemy behavior that could be most leniently described as complete bullshit.
Yet I can't help wanting to defend and recommend it, because it's something different. Even at its cheapest, most derivative moment, Kingpin is more interesting and fun than any number of well-made but run-of-the-mill shooters.