Painkiller is a very simplistic FPS, but what it does, it does very well.
You play as Daniel in 24 levels of in-your-face action, though the gameplay in Painkiller is different than most FPS games. The gameplay has you killing monsters that will try to take you down, and you proceed through the level by killing anything that moves. Whenever you start to battle with enemies, a heavy metal soundtrack kicks in, so you know you’re ready to dispatch some enemies. There are no friendly people in the game, and nothing to interact with. After you kill all the enemies in the area, a door or set of doors open that let you proceed through the level, and you must kill the enemies in the next area to proceed, and so on. It seems straightforward, but that isn't bad at all.
As I have stated before, this game is simplistic; there is nothing to interact with (such as finding a switch or button), no doors to open, no key hunting, nothing like that...no nonsense. There are also no cutscenes or voiceovers, or anything else to take you away from the action during gameplay.
That doesn't mean this game is easy, however. The gameplay pits you against many monsters at a time; so to combat them, Daniel is equipped with five weapons. This may not seem like a lot, but each weapon has a secondary fire mode, which almost acts like an entirely new gun, effectively doubling that number to ten. The most notable of these weapons is the Rocket Launcher / Chaingun, which just might be the most versatile weapon in any shooter I've ever played. There is also a Stakegun / Grenade Launcher. The Stakegun can pin enemies to walls, which is very satisfying.
After killing your enemies you can collect their souls. After you get 66 of them, you turn into a demon, and can basically rip apart your enemies just by looking at them and clicking. Souls also increase your health by one point, and while that may not seem like much, the average level has 150+ enemies.
The environments aren't what you'd expect. Sometimes you'll battle enemies in an opera house, or maybe an industrial complex. The different environments have different enemies in them. In fact, there are over 50 different types of enemies in the game, so repetitiveness isn't a problem. The bosses in Painkiller are truly unique. They tower many stories above you, and you will be literally looking up at a 45-degree angle to shoot at them. The bosses also give many memorable fights as they try to crush you or attack you in other ways.
Another aspect to the game is the Black Tarot Cards. Each level has specific requirements to it, such as collecting a certain number of souls, using only a specific weapon, etc. If you meet those requirements, you get a Black Tarot Card, which gives you advantages like slowing down time, doubling your firing rate, etc. You pick the cards you want to use before playing a level, but placing them requires money, which you earn by playing the levels. You can replay a level anytime you want, provided you have completed it. There is a lot of replay value to this game, thanks to the Black Tarot Cards and money collecting.
The graphics in Painkiller look very good, and it uses People Can Fly's proprietary 3D engine. This makes everything look extremely detailed, and it also has rag-doll physics, where enemies kind of flop to the ground using the built-in physics engine.
Painkiller's sound is also very good. Each monster has different growls and groans, so it adds some realism to the game. The bosses are also worth mentioning, as they fall to the ground once you've defeated them, and the sound almost shakes the ground.
Painkiller's Multiplayer is extremely fast-paced, and it comes with really cool play modes as well. There are the usual deathmatch modes and whatnot. One neat mode is the "People can Fly" mode, where the map is a cylinder and everyone is equipped with the Rocket Launcher / Chaingun weapon that has unlimited ammo. To score, you must use the rocket launcher to blast your enemies in the air, and then use the chaingun to kill them. The catch is that players only take damage if they're in the air. Another cool mode is called "Voosh,” where players are armed with the same weapon and unlimited ammo, but every minute or two, the weapon changes to another one selected by the computer for all players. The deathmatch in Painkiller is extremely fast paced, almost more than the original Quake. Almost all the time you are taking damage from enemy fire, but when you die, you almost instantly respawn, so the Multiplayer is definitely worth playing.
Overall, if you're a fan of FPS and you are looking for some gory, in-your-face nonstop action, you should look no farther than Painkiller for the PC.