USP: the USP has a light but you can only use this in the dark but unlike the M9 has no suppresser so enemy patrol near you will hear the sound of the gun but you can find a suppresser.
SOCOM: like the USP but has a laser sight.
Frag Grenade: anti-personal Frag Grenade, after pulling the pin you have 5 seconds before it explodes. Deadly!!
Chaff Grenade: intended to temporarily disable radio communications, as well as radar and other electronic devices. They cause no injury to any body, best used against CCTV and Cyphers.
Stun Grenade: this will knock out the enemy for a small amount off time this will alert them so its only best when you have an assault team on your arse.
AKS-74u: this gun is best used in the part of the game when you have to pose as enemy personnel, also good for cutting down the bad guys and a few shots will break through them shields that the assault team use. But ammo is spent fast so its hard to get into a shot-out unless you have a bandanna. You can get a suppresser for sum stealth fun.
M4: like the AKS-74u but much stronger you can shoot straight through bullet proof vest and shields but again ammo is spend very fast and no suppresser is available.
PSG1: well it's a snipe rifle but it's only worth using in a small part of the game the plant is just such a small space it's hard to use a gun like this.
PSG-T: good when you run out of ammo for the PSG1 but it fires tranquilizer bullets.
RGB: well cool when you're on alert you can stop approaching assault teams with ease.
Vamp killing tip: go into the corner where you pick up the RGB ammo and crouch and every time he gets close shot him with the RGB, if done correct you will not get hurt.
Nikita: fire this gun and you can direct your missile in any direction. Good for some fun
Stinger: point and shot simple as. Try holding up a guard with one of these