Ditto. I think you could work your way through most cable locks with vise grips or pruning shears given a little time. Go for a U-lock, or if it has to be something longer, heavy chain.

I've seen a couple of people here write that they used cable locks when touring so they could run in a store for a few minutes or something, but not one you'd want to trust for any length of time.

And $50 will get you a good U-lock.