Arborist's line, like Zing It, works very well.

There's a ton of paracord in all colors hanging in knots in trees all over Yosemite and the Central Sierras. I got a good indicator of how that happened once in an area where we could hang instead of using canisters. After teaching someone the PCT hang, when we got up the next morning they promptly snapped their cord snagging it in a tree against a knot. The broken rope rebounded and draped itself high over a branch.

I've used the Zing It a few times so far - it does not stretch and is designed to glide over bark without sawing into it, and the one time it did snag I was able to pull it out without difficulty.

Technically any cord will do, if you are careful. Mason line would probably work but knots easy and frays. I used to use a polypro rope from the hardware store but it started to wear with the dragging along the bark. I think the zing it will last for a long time, and has the added benefit of being much lighter and packing smaller to boot. You can order it online for twenty bucks a spool and it's useful for guy lines as well.