Pack Rat (Fallout: New Vegas)

Pack Rat is a perk in Fallout: New Vegas.

Effects
This perk halves the carry weight of items that have a carry weight of 2 pounds or less. All affected items in the game world will display their new lowered weight whether or not they are in one's inventory.

In Hardcore mode, this applies to ammunition weight, which could cause this perk to be especially useful, allowing the player character to carry twice as much ammunition at the same weight.

Bugs
There appears to be a bug related to Pack Rat in that due to the discrepancy between a follower's weight and the Courier's weight. The Courier is capable of adding an unlimited amount of ammunition into their companion's inventory despite the fact that it will exceed the companion's max weight i.e. 30,000 rounds of 5mm ammunition can be added if the companion starts out with room to carry an extra round, and the courier deposits the rounds in small amounts at a time.