These achievements/trophies are a little bit random as I was unable to pool them together into another category. Mostly they revolve around using performing other stealth-related actions such as turning off lights and disarming traps, but others require spending money, upgrading a weapon and accumulating a sum of military grade rounds.
Without further ado, here are the miscellaneous achievements/trophies offered in Metro: Last Light and a bit of information on how you can unlock each of them:
Description: Collect 1000 Military Rounds.
To unlock this one, you simply need to have 1000 military grade rounds in your possession at one time.
Collect 1000 Military Rounds.
Description: Make 100 Purchases.
Make 100 purchases at the gun shops in the Metro. The miscellaneous weapons are quite cheap, so be sure to buy them up when you are running low to add to your total purchases a little faster.
Make 100 purchases.
Description: Install all possible Customizations for a Weapon.
After acquiring a weapon, go to any gun shop and use the upgrade section to purchase and apply every available upgrade for your weapon of choice.
Install all possible Customizations for a Weapon.
Tesla & Edison
Description: Break 50 Lights & turn off 40 lights without breaking them.
As you progress through the campaign, you will frequently encounter light sources. You can turn these off in a couple of ways: either by getting close to it and interacting with them to switch them off silently or by using throwing knives or shooting them to break them. There are plenty of lights around so you should have no trouble obtaining these bad boys if you put your mind to it!
Turn off 40 Lights without breaking them.
Break 50 Lights.
Description: Disarm 10 Traps.
At various points during the campaign, you will encounter trip wires, usually connected to explosives. Moving into close range of the wire and interacting with it will disable the trap. Find and disarm 10 of these to earn the achievement/trophy.
Disarm 10 Traps.
Description: Fall in the Swamp 10 times.
During the Nightfall or Sundown levels simply walk/fall into the water so that a short scene plays and Artyom gets out by himself. Do this 10 times to earn this one.
Fall in the Swamp 10 times.