M2 flamethrower before level 65 glitch
A level 65 account to start with and another account that is at least level 4 are required for this hint. Go to your lower level account and go into Perk 1. Choose any perk, then go onto your level 65 account. Go into Perk 1 and select your Flamethrower perk. Return to your lower level account and you will find that you will have a flamethrower but nothing else unlocked, apart from the perks you already have. You can do this with any perk and can do more perks at the same time using the same tactic. This is useful if you want a flamethrower when you prestige, as you can get an account to level 4, put a M2 flamethrower, prestige and get to level, and transfer it again quickly.