The Good: Solid shooting mechanics, each level varies in art and enemy variety, each weapon is powerful and useful, huge tough boss fights
The Bad: Terrible CG cut scenes, story isn't used to its full potential, can get repetitive, very brutal on higher difficulties, no one playing online anymore
First person shooters have come along way, but People Can Fly showed the world that some times its better to go back then to move forward. You play as Daniel who dies in a car accident along with his wife. While she went to Heaven he got stuck in Purgatory and winds up getting involved in a religious war between Lucifer and the heavens. Lucifer wants to take over so Daniel is sent to stop him. While the story is semi-interesting is doesn't really go anywhere except for a few terribly made, low-resolution, CG cut scenes (I mean pre-PSX bad).
The game is all about shooting and it does it well. You get five different weapons through the game (I know very low variety) and you just blast hordes of enemies coming at you from all angles. Each weapon has a secondary fire like the mini-gun launches rockets, the shotgun has freeze shells, the stake launcher has a grenade launcher etc. Using both in tandem is important because certain enemies and situations will suit different weapons. Even the area you're in will affect this as well. The shooting is solid and fast paced and ammo pick-ups are a top priority. You can pick up coins which are used to be able to equip tarot cards that act as perks. These are also essential to staying alive especially during boss fights.
The game is really just shooting hordes (the AI just runs at you), but you can easily die due to sheer numbers. There's no cover, no special powers, just you and your gun. Every environment in Painkiller is very different so it's nice to always look forward to the next level. Not one is alike and even the boss fights are massive, tough, and rewarding to bring down. When you kill every enemy in an area the next area will unlock and you can move on. This proves a problem some times when there's on straggler left behind and you can't find him to move on. The little bit of platforming is floaty and badly done as well and should have been left out or tested a little more. While the environments and are looks nice navigating some of these levels can be a pain due to the terrible compass cursor and maze like hallways.
Another thing I like are the huge variety in enemy types. Some of the designs are crazy, gross, creepy, and downright weird. A lot of the time the enemies go along with the level, so it kind of feels like playing a pop-up book. The physics engine was highly regarded when the game came out, but seems dated compared to today. Over the years the game got visual upgrades, so I highly recommend one of the new versions which actually looks pretty nice for it being such an old game. The multiplayer is what kept people coming back, but you will rarely find anyone playing these days. Overall Painkiller is a great shooter just to kill things and shoot bullets. It's solid, smooth, and you can adjust the difficulty for every type of gamer.