I use a Kryptonite 1217 because it can go through the frame and both wheels while still having enough slack to attach it to almost anything. The bad is that it weighs 13lbs. I through it in my backpack and forget about it as I know there really is no better security I can get. (except the new york Fahgettaboudit chain). Just my .02 but I love my chain despite the weight and works great.

And just for reference as to its versatility.