HOLD UP! Wait just a minute! It seems I've forgotten a game... So, we'll take SWAT off this list, move everything back, and make this number 6...
6. Serious Sam
How in the ever loving fuck did I forget this gem? This is probably the most intense game I've ever played! It's a testament to the series that when I see heath and ammo I start to get nervous.
Serious Sam is hard.
Serious Sam is nerve wracking.
Serious Sam is had me more scared than most horror games I've ever had. But holy fuck, Serious Sam gives you the biggest adrenaline rush in gaming.
4. Painkiller
Painkiller is fucking mental. To quote Yahtzee Croshaw: "There's a gun that shoots Shurikens and Lightning." Yeah, that's right. Your shotgun's alt fire is to freeze people so that when you shoot them they shatter into tiny pieces. There's a stake gun the sends enemies flying through the air to be impaled into whatever surface you can think of. Also, as this was one of the first games to use Havoc Physics in a big way, enemies get knocked back 10 feet with every shotgun blast.
There are roughly one million different enemies to kill, and each have their own strengths and weaknesses - which usually involve killing dudes.
3. S.T.A.L.K.E.R.: Shadow of Chernobyl
Imagine that Fallout 3 had no levelling system or V.A.T.S. Imagine the combat system was replaced with excellent tactical shooting. Imagine the horror elements were ramped right up. Imagine it was tense and unforgiving, seeped in despair, and full of Russian culture and folk lore. Yeah, that's STALKER.
This is truly one of the most immersive experiences in gaming. You aren't a hero. You are a guy trying to earn some cash and survive in an area devestated by a nuclear blast. You collect artefacts, and do odd jobs for people. There is a story, but the meat of the storytelling isn't in dialogue, but in the world design. In the way the characters behave. In the little things you find.
Oh, and this is one of the scariest games I've ever played. Just wait until you're deep under ground in the pitch black and you start hearing noises...
Serious Sam looks fun, and that Shadow of Chernobyl monster invites a lot of euphemistic jokes I'm too classy to type.
those Stalker games rule. when i get a better computer I'm going to play them a lot.
When you get a better computer get the stalker complete mod!
Serious Sam is crazy. When I start to hear faint screaming, I'm nervous as hell. 
"aaaaaaah yourself." Fuck those kamikazes!
I want to play Painkiller but because there's like a ton of versions in Steam and i've heard some of them aren't that good, what's the version you would call the "definitive".
Painkiller: Black Edition. Most of the expansions suck, and Hell and Damnation leaves some really good levels out despite looking excellent.
I need to play Painkiller already. I'm pretty sure your tired of hearing that I haven't lol. S.T.A.L.K.E.R. sounds cool too. I might have to look into that one more.
Play both of them! ASAP! You own Painkiller, and I honestly feel like you'd love the shit out of it.
STALKER SoC and Call of Pripyat are the best PC exclusive FPS in years. Flawed, but still god-tier.
Oh yeah. Do you use any mods for either? I usually go for complete.
First Duke and now Serious Sam. You sir have picked two of my favorite FPS games because they were so wild. The Serious Samn PS2 game wasn't very good but I like it.
If you like either of those games I DEFINITELY recommend Painkiller if you have a pc.
I was a huge Serious Sam and Painkiller fan in the Original Xbox days. I played them both on PC too before they came to Xbox.
Wow. I didn't know Painkiller was on Xbox! Apparently it's also on androids...
It got rereleased for Xbox 360 as well. What happened to it's sequel Dreamkiller anyway?
It wasn't a sequel. It was made by another team and it was fucking dreadful.
I guess it was only on PC. I remember seeing it coming for Xbox 360, but I think it never did. I would've bought it anyway.