Strange that the wired 360 isn't working for you. I've used my wireless one just fine, using the USB PC wireless adapter for Xbox 360

Any bluetooth controllers?

Have you used them with other Android TVs? I'm not familiar offhand with whether any of those work on Android TV; I've only connected, say, PS3 or Ouya or other bluetooth or Android-specific controllers

Nexus player gamepad

Someone else recommended this a couple weeks ago. I picked one up at it works great. https://www.amazon.com/dp/B01EO5QPN2/ref=cm_sw_r_cp_apa_gPDhybGCERJN1

The Ipega PG-9023 bluetooth controller works great with android. It also doubles as a great portable controller for phones and tablets (pretty much turns your device into a portable game unit). I've used my phone, nexus 7, nexus 9 in it and works great. Works on my Android TV too.

Literally 99% of them. I dunno how you even got a Gamecube controller to plug into it though. That's pretty strange. And what "off brand" gaming controller? Is it USB or Bluetooth?

This is the one I'm using: https://www.amazon.com/Buffalo-Classic-USB-Gamepad-PC/dp/B002B9XB0E/

Works perfect with RetroArch, and a few other games/emulators I've thrown at it.

I got this Controller and it works well, the only issue I have is that there is a small lag when using it with Retroarch that I have not taken any time to troubleshoot Otherwise I've used it with Real Racing 3 and Beach Buggy Racing without issues

8bitdo makes some pretty dope and faithful retro reproduction gamepads if that's your thing. A bonus is that they're wireless and use Bluetooth too, along with having Android functionality built in. They just released an N64 model a few days ago and it looks pretty legit.

Gamesir G3s won't work with Modern combat 5 or Shadowgun. Heck it doesn't even work with Asphalt extreme. Works alright with emulators though. ANyone got the G3s working with MC5 and asphalt extreme on the Mi Mox 3s?