I'll keep it simple, has anyone tried using anything that isn't the official gamepad with the Nexus Player?
I was thinking about trying this:
Patec® Bluetooth Gaming Controller Joystick Gamepad for Android Smartphones and Tablet PC - Black by Patec Permalink: http://www.amazon.ca/dp/B00JDC5NJ4
Edit: Found the amazon reviews of an identical product by the same product, some say it requires an unnecessary app... so I'm wondering if I should run for the hills on that particular product: http://www.amazon.ca/Bluetooth-Wireless-Controller-Gamepad-Joystick/product-reviews/B00JDC5OKW/ref=dpx_acr_txt?showViewpoints=1
Any standard Bluetooth controller will work.
Also Xbox 360 controllers work out of the box. USB OTG or wireless if you plug in the wireless dongle. The downside is that there is no "back" or "home" button mapping so you need to use the remote to exit apps.
PlayStation 3 & 4 controllers work as well but require a special program and could lead to instability and heartache.
I'm using two Nexus Player controllers and two Xbox 360 controllers on mine and it works great for 4 player games and emulators.