Kryptonite New York Fahgettaboudit U-lock, $89.95 Pertinent Thickness: 18 mm Shackle Weight: 4.6 pounds Free Anti-Theft Warranty: $4,500 for one year
If I were a pro bicycle thief, I'd skip any bike protected by a poison-frog-yellow New York Fahgettaboudit U-lock (or the NYFU). It took its beating with the poise of a journeyman NHL defenseman. At my hacksawing rate, it would have taken 42 minutes to cut through the 18 mm shackle. (It didn't get a perfect 20 score for security because my assault managed to jar a spring loose inside the crossbar, but that wouldn't affect lockup strength.)
I wasn't too surprised: The NYFU is made with so much hardened steel that it could moonlight as a dumbbell. But weight aside, its small size makes it easy to carry. The only drawback of "mini" U-locks like the NYFU is that the small stature means you can only lock the bike frame to an object—there's no room for also locking wheels. Kryptonite has enough confidence in their new flagship lock to back it up with a $4,500 anti-theft warranty. (Not that I've ever seen, much less owned, a bike worth anywhere near that much.) It's pricey, but the NY Fahgettaboudit is worth the dough.
Portability/Ease of Use: 7