Kona II: Brume

To be clear this says "find all weapons in the game" but you only need one of each, so you don't need to collect every single weapon in the game, just one of each types so don’t worry if you skipped one

They are:

Revolver:
You can this at the very beginning of the game in the cabin in one of the drawers

Can be found in the basement of Hamilton’s mansion in a yellow toolbox next to the small elevator shaft door

Can also be found in the hand of the security guard that crashed his snowmobile when arriving in Eweewach Valley

Hatchet: Can be found in the same cabin as the revolver at the very beginning of the game on the pegboard above the workbench

Can also be found outside the second cabin half buried in snow at the beginning of the game (the one who doesn’t have a watch tower next to it), east of the frozen security guard and the wooden bridge along the frozen lake

Can also be found outside other cabins throughout the game, usually on a log

Rifle: can be found in Hamilton's hunting room in the mansion (the same room where you fall through the floor into the flooded basement)

Can also be found in the bathroom on the second floor of the old house in Leech Lake

Shotgun: Can be found over the fireplace in Hamilton and Cynthia's secret cabin on the very first island when arriving in Leech Lake

Mistanite phaser: This is story related and cannot be missed, it is given by Jules Demers after completing the mine and collecting enough mistanite around the map at the end of the Leech Lake quests