Poncho (3.5e Equipment)
From D&D Wiki
A poncho is a blanket term for any clothing meant to keep the wearer dry. If a character wearing a poncho is caught in the rain, they remain dry for forty rounds of exposure. If they leave the rain (Step under a tree, enter a building) the water will sheet off of them, returning to its dry state in three turns.
Weight: 2 lbs
This piece of clothing was an essential for one of our groups' characters, a female mage, who was a magical Aquaphobia, meaning she would sublimate when water touched her, causing her 1 point of damage per turn.