There are 10 weapons in Tormented Souls 2. Collecting all of them in a single playthrough unlocks the Hoplophile trophy and achievement. The last weapon, the Electric Lance, will only appear after clearing the game once so you can’t unlock the trophy on your first playthrough.
For the 5 weapon upgrades refer to Tormented Souls 2: Weapon Upgrade Locations.
Weapon #1: Nailer
Story-related, cannot be missed. Combined the Compressed Air Canister with the Nailer Frame. Both these items can be found in the Workshop in the Convent.
Weapon #2: Hammer
Story-related, cannot be missed. On a nun’s corpse in the Crematorium in the Convent.
Weapon #3: Shotgun
Complete the puzzle at the top of the Bell Tower in the Convent. (see Bell Tower Puzzle)
Weapon #4: Automatic Nailer
On a corpse in the male bathroom in the Lower Floor section of the Mall.
Weapon #5: Crowbar
Story-related, cannot be missed. On a man’s corpse in the Bathroom in the Processing Plant.
Weapon #6: Crossbow
Story-related, cannot be missed. Pick up the Metal Bike Parts in the Surveillance Room of the Processing Plant, as well as the Crossbow Frame in the 2F Kitchen of the Processing Plant then combine them.
Weapon #7: Chainsaw
Story-related, cannot be missed. Pick up the Circular Saw Blades that drop after defeating the Harvester and the Chainsaw in Reception after going down the ladder in the Slaughter Room, then combine them.
Weapon #8: Hand Cannon
Complete the puzzle in the mausoleum in the Cemetery Grounds. (see Reliquary Puzzle)
Weapon #9: Sledgehammer
Story-related, cannot be missed. In the Cave next to Joseph.
Weapon #10: Electric Lance
In the Workshop in the Convent, after beating the story at least once.
As of Update: 1.004.000, the Electric Lance has been removed from the game temporarily.
More Tormented Souls 2 Guides:

Dark says
I have completed the game once but the electrical spear is not in the workshop on second playthrough
PT says
I dunno why I got electric lance at first play though at the beginning of the game
Otaku_Prince87 says
I finished my first playthrough with the good ending and no electric lance but I still got my new outfit.
Jack says
Same. What rating did you get? I had a C. Maybe too low?
ObsiEez says
The most recent update has removed it from the game since it was accidently added early
Boris R says
Is it official that there are only 10? Or do you unlock something with an S rank on tormented difficulty?
Anankha says
The Lance being available was a mistake so it was taken out by the devs.
It’s certainly not unlocked with an S rank on Tormented difficulty.