I just played the game for the first time. It really is a masterpiece. I'm not just saying that to look like a cool jerk or similar Newgrounds stereotype. It's actually an entertaining, well-programmed game with some funny speech if you talk to people before shooting them. An example of the good programming: you can talk to people calmly, but if you shoot in the same area as them, they'll start to flee from you.
I could have easily opened up Flash, made a poorly programmed game, and got the same attention as Pigpen, but this guy actually put some effort into making it a quality game.
That quality is respresented by the high score the game gets, despite being hugely offensive. I mean, to get over 3.0/5 for such a mass-offending game is really quite remarkable.
And that's why the game is at the top of my favourites list on NG ;)