Locks that work

I know this is sort of the opposite to the point of the thread, but what do you think the lightest/smallest lock you could get is?

...

As light and small as possible please.

The obvious choice is the Kryptonite Evolution Mini, or a motorcyclist d-lock designed for disc brake....

Cheers for the reply. But I think you've misunderstood.

There is no way I'm carrying a d-lock to go on a nice long country ride. Especially not a kryptonite. But I think I've found a style that makes sense:

Small enough to fit in a jersey pocket or saddle pack. Combination lock, so other people can unlock it. Plus if I get one of the longer cables it will easily be able to wrap a few bikes to something.