Call Of Duty 5 : World At War
This perk is unlocked at level 40. It will give any weapons in the loadout it is used with the maximum amount of reserve ammunition you can carry. It's best used with high Rate of Fire weapons that tend to use up the magazine faster than they do damage to the target. A good example is the PPSh-41. The gun has an extremely high RoF, meaning it would use most of the magazine before doing any effective damage, so more ammunition is needed than normal. Bandolier can remedy this. It is also good for weapons that have a low ammo count to begin with, such as the Thompson. Combine this with the Extended Magazine attachment (The Round Drum to be more specific) for this item, and it will maximize the weapon to a good potential.
Bandolier is also good for long ended matches, such as "Hardcore Team Deathmatch". If you are careful and maneuver yourself efficiently, then you can last for a long life, and if you don't have this perk activated, then you might find yourself out of ammo. Keep that in mind because in 'Hardcore, your HUD is removed, which means no ammo count. Bandolier eliminates the worry over whether ammunition is running low.
Bandolier is good for any SMG with an Extended Magazine, and any MG, especially the MG42 and FG42, seeing as those guns consume ammunition very quickly.