Poncho Liner, Ranger Blanket, Woobie. No matter what yo call it it is one of the most loved piece of kit there is. These are in the old school cam that I remember when I was in the regiment and was the MUST have piece of kit, with a few upgrades.
This Woobie has the zippered head hole to make it that much easier to wrap around you in or out of the rain. Tie downs have triple the normal sew on spots to ensure they stay for years to come.