Combination locks offer one distinct advantage in that being key-less there are no keys to lose.
The Street Quantum from Masterlock offers a usable 1.8 metre length, plenty for wrapping through the frame and wheels of most bikes. The seatpost mounting bracket is neat and simple to fit, and at just 590g including the bracket, it's fairly lightweight.
Unfortunately, this light weight is a tell-tale sign of the lock's performance against attack. In our first round of tests the Quantum was cut through in just 2.8sec with our budget 2ft long bolt croppers, the cable inside the plastic coating being closer to 8mm thick than the 12mm width stated.