Left 4 Dead 2

The 8 weapons you need for this are listed down here below and where to almost find them Everytime

The machete and the frying pan can be found on survival parish- bus depot

The axe and the crow bar can be found right at the start of

The cricket bat , katana can be found on survival dead center - mall atrium

The electric guitar can be found fast on both survival and campaign level of dark carnival - concert

And lastly the nightstick can be found in the campaign chapters which are in the parish - you'll find one easy by killing zombies and looking for what they drop

This is my first solution so if you like this please comment or thumbs up thank you :)

The full list of available melee weapons is below. Most of the time, it's up to luck as to which weapons you find where, although there are some which can be found in certain spots (see link below).

Axe
Cricket Bat
Crowbar
Electric Guitar
Frying Pan
Katana
Machete
Nightstick

Note that the Golf Club is only accessible with The Passing DLC and isn't required for this achievement.

If you're having difficulty locating a particular weapon or you just want to find out more, check out this wiki page:

http://left4dead.wikia.com/wiki/Weapons#Melee_Weapons