I use the Kryptonite New York Fahgettaboudit on my most expensive bike when I ride it, but its use depends on knowing exactly what it is going to be locked to. In other words, the U lock is so small it only works on certain racks. If I'm going somewhere in town where I don't know what type of rack will be available I use the longer "stretch" version of the Kryptonite U lock because it allows for differences in rack design and size.