This is how you can make somebody not get anything but perks. Also, this isn't really a cheat, it's more of trick.

First, make sure there is a death machine perk around. Have a player grab that.

Then, have them buy a perk while they have the Death Machine. Note: The DM has to be almost expired. Like it has to be blinking 3 flashes per second.

Finally, the person will only have the gun they had out before they grabbed the DM perk!