All the melee weapons are on the first level, and you’re looking for a wrench, bat, rusted pipe, and a katana. You don’t have to score a kill with these, you just have to have held them at one time or another.
Wrench: Near the beginning of the level when the game tells you about the melee combat and movement. Press to pick it up from in front of the boarded up doorway you have to smash through to continue the game.
Bat: Just after you picked up the wrench you’ll come to a large hole in the wall you have to go through to progress, where the body falls in front of you. Go through the opening and up the hill then turn around and look in the right corner, next to the white door is the bat. Hang two rights through the doorway on you left to get to it.
Rusted Pipe: Immediately after getting the bat you’ll have to turn a wheel to stop poisonous water form blocking your path. After you’ve done that you’ll see a body at the end of the hall, next to it is the rusted pipe.
Katana: This is located in the are where you have to climb a flight of stair to knock off a couple of explosive barrels to take down a wall so you can progress. There are two areas where you have to go upstairs to the third floor, and the katana is in the first area. When you are on the top floor and see the barrels dead straight ahead of you, you should also see a large doorway on you left (a room with the light out). Back behind that is another room, you should be able to see if not it’s on your right. Use the alien vision to see in the dark if you need to. In the back left corner you’ll see a light over another body, beside the body is the katana.