Kryptonite

Kryptonite New York Fahgettaboudit Chain with Disc Lock (5 Ft)
$154.95
This lock will deter any potential thief. There is no way anybody will be able to break through this lock without a cutting torch. The only drawback is its quite heavy, so don't buy it if you are planning on carrying it with you. Great for at home or at work.

Kryptonite Evolution Series 4 Standard Bicycle U-Lock with Bracket (4-Inch x 9-Inch)
$70.85
This is the worst lock I ever used. I got this lock because it is long enough to lock two bikes, but the key is incredibly difficult to properly seat in the lock and turn. If you want to have to fiddle around every time you need to lock or unlock your bike, this is the lock for you.

Kryptonite
$0.99
We see ourselves through Superman, the perfect man struggling against our deepest fears. His fears, truly our terrors, connect with that part of you that goes numb when you see Truth.

Kryptonite Kryptolok Series 2 Standard Bicycle U-Lock with 4-Inch Flex Cable Bicycle U-Lock (4-Inch x 9-Inch)
$44.65
This is my second lock from Kryptonite and they are they only brand of bike lock I will use. I've had my bike lock for 2 years now and have never had any issues. Easy to use, this one is especially nice because it comes with an attachment so you can secure your lock to your bike while you ride and the cord allows for greater flexibility in where you can lock your bike up. I highly recommend!