Short version
#1 Blaster - Ammo Saver
#2 Super Shotgun - Kills things around corners when walking through a map
#3 Machinegun - Used for killing most things
#4 Hand Grenade - Used for Killing things around corners without being noticed by other monsters (usually)
#5 Grenade Launcher - Used for Killing things around corners, or on a platform above you
#6 Railgun - Used Mainly for Icarus, or other monster far away
#7 Rocket Launcher - Same Role as Railgun, but has spread damage. Parasite killer in the Lab.
#8 Chaingun - Boss Killer
#9 BFG10k - Guard Swarm killer
#10 Shotgun - Good for Unit 1
#11 Hyper Blaster - Last resort weapon against melee



Detailed version
#1 Blaster - On the top because it has infinite ammo, and has long range without losing power over range. The other guns are useless if you run out of ammo. I use this very often to save ammo for the tougher enemies. I usually pick off one enemy at a time.
I usually use the blaster on Icarus if I don't have a railgun, and when the Icarus get close I either use the machinegun, or super shotgun. (usually the super shotgun to see the Icarus go flying though)
It's also good for exploiting stationary monsters that wont attack back because you are at the correct angle behind a wall.
I almost always use blaster on berserkers, light guards, iron maidens, brains, baracuda (shark/flipper) and tanks if I try to conserve ammo for tougher things.
I don't use blaster on Shotgun guards, machinegun guards, Gladiators, gunners, or mutants(unless the mutant cant get to me).
Blaster is good if you have room to hit+run a lot.
If you use the blaster on easy stuff, then you'll never have to worry about ammo when you really NEED the ammo.
#2 Super Shotgun - Placed second because if there's an enemy around the corner that will surprise me, I can stun/kill it with the super shotgun, and it does high damage. There's also a lot of ammo for shotguns.
This is one of the 2 main weapons I use for killing Gunners, gladiators, technicians. The monsters are usually very close to you anyways, so a large portion of the game you use this gun.
I always use this on Mutants, Huge "hit box", easy to dodge the "pounce", takes 3 hits to kill with super shotty. Shoot once, causes it to go into hurt frames, shoot again it's almost dead, hide a second shoot it again to kill it, if you mess up, it'll be sent into hurt frames instead of attacking.
#3 Machinegun - Placed 3rd because of the ability to save bullet ammo, kill fast, and send things into hurt frames easily, without having to go up next to the enemy like a super shotgun.
I use this for medium range combat. Bullets are very abundant, and machinegun is good at killing things fast without wasting tons of ammo like the chaingun.
It's the most effective thing to kill guards without risking hurting yourself, or using a BFG10k which takes a lot of cells. The reason why, is because when you get swarmed by guards, you can send them all into their hurt frames, and kill a couple, then hide behind the wall for a second, then when you go back out you can finish them off.
#4 Hand Grenade - Placed 4th because it's used for killing things without other monsters noticing, and kills stuff around the corner. This will save a lot of health and armor for you.
This is one of the 4 things that can get you out of a lava/acid pit (hopefully you use invulnerability, and you may need quad damage for an extra boost)
#5 Grenade Launcher - Ranked 5th because It's like a hand grenade, but for when you need to kill something fast, but still need to use a grenade.
When you need to kill something around the corner fast that's chasing you is a good time to use it if you don't want to use the super shotgun. Or you cant time a throw to go high enough to get on top of a platform. This is one of the 2 main weapons I use for killing gunners, gladiators, technicians.
This is one of the 4 things that can get you out of a lava/acid pit (hopefully you use invulnerability, and you may need quad damage for an extra boost)
#6 Railgun - Ranked 6th because it's a sniper. High damage, Long range, but it doesn't have much ammo, and if you are close to an enemy, it's better to use a super shotgun. Only good for killing far away monsters, or if you don't feel like using the machinegun or super shotgun on a gunner.
I mainly use this for the Icarus, because they take a lot to take down, and are usually far away. Every now and then I will use it on gunners. In the 9th unit I use it to kill 2 Tank Commanders at the same time since railgun goes through enemies. It's low on the list because there's not that much ammo for the railgun. I rarely ever used it, and it didn't get to 100 slugs that it could have gotten to.
#7 Rocket Launcher - Ranked 7th because it's basicly a replacement for Railgun untill you get one, and it has low ammo as well. There's a couple exceptions where I'd prefer rocket launcher over Railgun. Usually it's guards being up on a cliff in Unit 9 that I can't see, and want to kill them all in one shot that I use this.
This is one of the 4 things that can get you out of a lava/acid pit (hopefully you use invulnerability, and you may need quad damage for an extra boost)
If I'm in a rush, I use rocket launcher on tanks.
It's also good in the lab area for killing the duos and trios of parasites.... if you know where the parasites are going to be, so you don't blow yourself up.
#8 Chaingun - Ranked 8th because I only use it for Boss Battles because it kills things really fast, but for anything else it's pretty useless because it uses ammo WAY TOO FAST.
If I find an abundant amount of bullets, with a bunch of strong enemies nearby.
#9 BFG10k - Ranked 9th because it's mainly used for whenever there is a ton of machinegun and/or Shotgun guards, since they will all die fast, and would probably lower my armor really fast anyways if I used any other weapon. The BFG10k is usually used only in Unit 9's first map, but there's exceptions. I don't like using it because it using up Cells that power my power shield.
This is one of the 4 things that can get you out of a lava/acid pit (hopefully you use invulnerability, and you may need quad damage for an extra boost)
#10 Shotgun - Ranked 10th because it's useful for early levels, However, after Machinegun it doesn't get used as much because there's plenty of bullets around, and you need to save up shells. After Super Shotgun it is never used.
#11 Hyper Blaster - Ranked 11th because I don't use it, doesn't kill fast enough for me to want to lose the cells that power my power shield.
I'd only use it if i had no bullets,shells, or slugs, and I'm stuck against the wall with a melee monster.



Basicly what I use is dependent upon the ammo around me. Since there's usually not many rockets or slugs, and I save Cells for Power shield, I use super Shotgun and Machinegun the most. Then I use grenades and the blaster for just about everything else. Rockets and slugs I save for emergencies, or for Icarus.

That's my list, let's see your list. =)

#1: Machinegun
#2: Super Shotgun
#3: Hyperblaster
#4: Railgun
#5: BFG
#6: Blaster
#7: Rocket Launcher
#8: Shotgun
#9: Minigun
#10: Grenade Launcher
(#11: Grenades)

#1 is the gun I have in my hands the most, easy on ammo, decent fire-rate and damage, an all around good weapon.

#2 is probably the one I kill the most with, as it is great for those melee-attaking bastards.

#3 is really quite simple, it's a minigun with less ammo consumption, quicker firing and more damge. Plus mosters are too dumb to really try and avoid it.

#4 ahhh, the Railgun, who DOESN'T like this gun, it's so powerful, fast firing and just pure awesome. Ammo is a bit scarce though.

#5 time for the big freaking gun... 10,000 that is. I know, it burns up your ammo, but it's awesomeness (especially with EGL effects on) has me always looking for a chance to dust it off and fire a round or two.

#6 the Blaster is practical and simple, fire and then keep firing till it's gibbed, but horrible for power, fire-rate and creativity. So I never use it in combat.

#7 the RL, a symbol of Quake known worldwide by gamers. It's hard to find an FPS without one of these. I tend not to use it due to it's unoriginality, but sometimes when I feel like some gibs raining down on me, I'll yank it out.

#8 the Shotty, good in the first few levels, ignored from then on.

#9 the minigun, or as it's more incorrectly known, the chaingun. Fun as HELL but burns through your ammo almost as fast as the BFG and with less satisfaction. Also it takes to long to start firing.

#10 (and 11) both suck, sometimes, if you KNOW a Strogg is there, but it doesn't see you, you might use a grenade, but it's more fun to run up with the Super Shotgun.

1: Rail Gun - Speaks for itself.
2: Minigun - A very reliable lead blender.
3: BFG 10K - Huge burst damage but slow to start off
4: Hyper Blaster - Energy blender. This would be higher on my list if the cooldown time weren't so horrendous.
5: Super Shotgun - Love this gun. Lots of burst damage with an abundant amount of ammo that you can run around and tag strogg with, without being subject to self damage.
6: Rocket Launcher - Nade launcher. Cept it fires straight. Can't go wrong there.
7: Grenade Launcher - I like using this gun for killing off strogg in corners for when your health is low and/or to conserve ammo for other guns.
8: Machine Gun
9: Shotgun
10: Blaster - It's infinite. Garbage damage and not hitscan. Sad face
11: Hand Grenades (sometimes I'd rather just use the blaster even when the nades do far more burst damage.. they just are such a pain to use.)

Even if I couldn't hit a barnyard door with the railgun, I'd still put it in that spot just for being one of the most badass guns ever made for a shooter.

1# railgun --- because it's powerfull than rockets,shells,grenades; i can kill gladiator with 3 rails instead of 4 supershotgun shots, medics with 2 rails instead of 3 supershotgun shots and more
2# hyperblaster --- because it's again powerfull but it uses cells
3# supershotgun --- i use it for almost all monsters but is weak than railgun
4# grenade launcher --- i don't use it very much but i can use it to kill monsters around corners
5# machinegun --- it's pretty good but not powerfull
6# rocketlauncher --- because i kill swarm of weak enemyes
7# hand grenade --- it's same with grenade launcher but less speed but i can cook it for a fast speed or for fast explode
8# BFG10K --- i use it for tough swarm monsters but there aren't very much swarm monsters in game
9# chaingun --- powerfull but a "Bullet Parasite"
10# shotgun --- good for unit 1 monsters then second weak weapon
11# blaster --- i don't use it because in level outer base there is a shotgun and blaster is the WEAKEST weapon