Fist of Zeus!!
This thing packs down smaller than my fist but packs a huge punch. It always lives in the bottom of my pack tied into the end of my rando line with a DMM Bugette and CAMP Photon clipped to it. If I find myself getting into a situation that may require roping up I just pull on the knot in my pack and boom, out comes the whole setup. No digging around or losing crucial pieces. It is light enough that it guarantees itself a spot in my gear list since I don't have to feel bad about the weight of it keeping my slow moving on the uptrack. Like Tris said, you wouldn't want to hang around in it all day, but you can rest assured it comfy enough for some raps and belaying.
PS. Tris is my ski partner.