Kryptonite locks from several years ago suffered from Bic-pen opening methods, and have been updated accordingly. Some were also subject to jacking them open with a car jack.

Masterlock is a fairly well known brand in general locks, but their bicycle locks that I have seen didn't look too impressive, and seems like I didn't see them at bike stores, either.

All of them can be cut open with power tools or torches. From what I've seen the warranties against bike loss are fairly useless (overly restrictive).