As part of my "Welcome to Nexus 6p" kit from Mobilezap, a USB Type-C 3.1 Male to USB 3.0 Male Cable!
We are all used to cheap, commodity, (essentially) disposable USB cables due to their unreliability. The game changes with the USB Type-C standard and not just any cable is going to work. The standard requires a resistor value of 56k Ω as a pull-up on the configuration channel when used in a Type-C plug to a USB 3.1 Type-A plug assembly.
Based on extensive tests by Googler Benson Leung, a lot of cables out there are non-standard and can cause damage to your devices. This is not limited to cables but also converters as well.
I did my testing using the Nexus 6p itself, following a method outlined by Geoff Hoff, by running the following command:
adb shell "cat /sys/class/typec/typec_device/current_detect"
Based on my testing I have been using the Mobilezap USB Type-C 3.1 Male To USB 3.0 Male Cable for almost a fortnight with no issues. The cable is available here for $26.99.