Abus Bordo is excellent and small. I used it for 3 years in the middle of Frankfurt, where bike theft was/is high. It can be subjected to prying attacks.

I currently use a Kryptonite Evolution Mini 7 because bicycle theft is even higher here than in Frankfurt and I wanted the extra security but it is much more cumbersome and heavy than the bordo which is excellent for its weight/size.

Those thin cables in this thread look like **** and will last two seconds as I could clip them and get on the bike in one motion without anyone being the wiser. Use at your own risk.