Gunslinger

Gunslinger is an achievement/trophy in Metro Last Light.

Overview
This achievement is awarded to the player for killing at least one enemy with every single weapon available in the game. That includes all guns, your knife, throwing knives, claymore mines and the two types of grenade. It can be a kill on an enemy human or a mutant. Note that all small non-hostile mutants, such as mutant crows and hatchling shrimp do not count - due to a glitch, Spiderbugs do not count either. Below is a written guide for a foolproof way of getting this achievement/trophy without missing a weapon. Alternatively, refer to the list of Last Light weapons as a checklist of weapons. Note that DLC weapons, including the RPK-74 and the Abzats Shotgun, VSSK Vychlop and the DShK 12.7mm Machinegun do not count.

Location Guide
The following guide is for Ranger Mode (2 guns), attempting Shadow Ranger, Invisible Intruder, Invisible Man, Invisible Savior, Invisible Soldier and Rain Man  achievements/trophies, and only using weapons found in the Metro, none that have been bought. The guide contains spoilers.

Sparta
Take the Valve and Revolver with you to the surface.

Ashes
Kill the Watchmen with the Revolver and Valve.

Torchlight
When Pavel asks for help with the grate, there is an Ashot with an extended barrel and a Lolife nearby (this may require a bit backtracking) - pick them up.

Echoes
Do not get the Duplet here, just stick with the Lolife and Ashot to kill the Watchmen.

Revolution
Check the locker when you retrieve your gear: there is a Kalash here if you look carefully. Inside the room where the workers are doing a service check, there is a Tikhar up the ladder on the right as you enter, follow the pipe above the soldiers and turn left, it is located at the end of the catwalk - pick it up.

Regina
Inside the flooded room to the left there is a Bastard. Swap it with the Tikhar.

Keep going. Just before where you need to push the abandoned metro trains with Regina, to the right there is a room (a Watchman will run into this room when you approach, so look for that). Kill the Watchmen here with the Kalash and Bastard. Inside the room there is a Shambler. Backtrack to get the Tikhar.

Keep going. You will be attacked by Watchmen from behind - kill them with Tikhar and Shambler, and wait for one to jump on Regina to knife it.

Bandits
Near the end where you have to ring the bell for the boat there is a quad-barrel Duplet up stairs - use it to defend  against the Nosalis while waiting for the boat.

Sundown
Use grenades, incendiary grenades and Claymore Mines to kill the shrimp. Incendiary grenades will instantly kill any shrimp. The big Shrimp will take more than a grenade to take down so fire at it first and lay down Claymores while backpedalling.

Pick up the Kalash 2012 here in a house near the red missile.

Nightfall
Kill the Watchmen here with the Kalash 2012.¨

Undercity
In a room where there are a few Nosalis eating the bodies, look up - there are Winged Nosalis hanging bat-like to the ceiling. One throwing knife to the torso should kill it silently.

Contagion
Enemies here carry the Saiga - knock them out and pick it up. There is also a Helsing on a table in a room with a lot of bodies on the second floor.

The Crossing
Kill the Watchmen here with the Saiga and Helsing. Pick up the VSV near the ladder toward the end.

The Dead City
When you see the vision of being hit by a car, kill the Watchman with the VSV. Immediately walk to the left and into the house. There is a corpse clutching a Preved in the bath tub on the second floor. Kill the Watchmen here with the Preved.

D6
As soon as Artyom has access to use the Gatling you must kill regular soldiers before the riot shield guard and flamethrower heavy, as they do not count as a kill. As soon as you kill one soldier with the Gatling, the achievement/trophy will unlock.