Sitting in a tree is not hunting... it is not even sportlike. Planning on throwing corn under the tree too?
Hunting is finding a trail, tracking the product, getting close to product without scaring, and taking said product in a humane way. If you really want to hunt, use only a bow or knife. (Damn redskin [I'm sorry.. NATIVE AMERICAN] friends have ruined me huh... Thanks Yahzee)
Not sitting in a tree, not taking a 800 yard shot from a blind with your ubernew space scope, not fedding the animal to fatten it up before you pet it and shoot it... 6 times because you forget where the heart/lungs/etc were.
But, to answer your question, if you want to sit in a tree without a stand, use a loggers rope.