@IceBeam
"it has already been proven that Survivalist is always suboptimal and weaker than any other perk." LOL, sure dude. I've read that "proof" before and it's nonsense. It completely ignores the advantages that survivalist has.
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One of the main things that makes a perk good is how easy is to finish a match.
Survivalist can survive mistakes that would normally get you killed. And if you're someone who doesn't make mistakes, you already are winning 100% of your games anyway.

I'm not an amazing player, so I make mistakes. I haven't obsessively memorized the spawn locations, and I'm not great at kiting. I often get surrounded, or even accidentally rage a scrake with a stray shot when there are fleshpounds after me. Suffice it to say, I need some additional survivability to complete HOE matches. Survivalist gives me exactly I need.

Survivalist has 25% damage resistance, 125 points of heavy armor, a greatly buffed healing syringe, and healing grenades. This allows it to take a massive amount of damage, only beaten in this regard by zerker and medic. SWAT is inferior at this because after it loses its 150pts heavy armor it has zero damage resistance, and only has the regular syringe.
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Another reason I play Survivalist is because of my preferred choice of weapon, the SPX.
This gun is fucking amazing, its my main gun from wave 2 onward (although I usually grab either an RPG, stoner, railgun, med shotgun, or UMP to supplement it, as well as a med pistol)

Shouldn't I be playing Sharpshooter or Gunslinger then? No, and here's why:

Sharpshooter lacks a perk to increase reload speed, which immediately kills using SPX as my main weapon, and most of its perks involve standing still and crouching to increase damage. It also has absolutely nothing to increase survivability, so its very, very easy to get killed.

Gunslinger is much better, but still has some problems. The movement speed is awesome, and the extra damage helps shots-to-kill against large zeds in 6p HOE. The problem is that it has nothing to help it tank damage, so I find myself dying very quickly when playing HOE. It also lacks a perk to increase ammo capacity, so I always run out of ammo in my SPX before the wave ends, and have to switch to magnums.
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Also, spontaneous Zed-plosion is a fantastic perk, especially with the SPX. It has saved my ass so many times when I'm surrounded, and it helps in killing groups of enemies. This perk alone is well worth having only +15% damage instead of +25%.

Another plus is that survivalist is a good secondary medic with the improved darts and healing grenades.
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When I first started playing KF2 a year and a half ago, I believed all the shit about survivalist being a horrible perk, up until recently when I've started actually using it.
It's survivable and versatile, it fits its role perfectly. As survivalist, I'm anything but deadweight in multiplayer, usually topping the kills in addition to being a supplemental healer.

It's funny how the first advice you salty assholes give to new players is not to play survivalist. It's by far the best perk for new players because it allows you to explore a variety of playstyles while giving you the tankiness you need to survive as a new player.