For early purchases the MP5 is the first reliable gun, it'll save your life. The weak flashlight is the only melee weapon you'll ever need. Once you have those two things you'll do so much better. Personally I prefer slower-firing automatic weapons to land consistent headshots and not waste ammo, so to upgrade the MP5 I'd go SigSauer>Tommy Gun>AK47>G36>AA-12, which is an auto-shotgun that one-shot-kills up to like wave 17. Add a FnScar for long range once you have the money
Best run is 20th wave, like 72 minutes. I made over 10k. Stealth is your friend, crouching makes you near invisible to zoms. Take things slow and careful and don't use the Enfield unless you're on a building cause it's super loud!
Some tips: If a zombie hasn't detected anyone, the silenced pistol and melee weapons will do double damage. That makes the pistol one-hit-kill any zombie 'til about the 4th wave, and the fire axe one-hit-kill anything for as far as I've gotten. However bladed weapons like the fire axe don't stun which makes them super hard to use once a zombie detects you, though a careful mix of right-click and left-click fighting can make them viable. Go for blunt weapons if you don't plan on using stealth. You can hold the attack button down with a melee weapon to continuously attack. When using sandbags and other fortifications, it's best to not completely block paths. That just means you'll have less escape routes and a bigger hassle to get into your base. Rather, try to place them around doorways with small openings for you to squeeze through. Zombies will just bash fortifications instead of walking around them, so smart placement can stop most zombies without hindering you.
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