Change controls on the fly
One of the most frustrating things about switching off with a friend is having to head to the "options" or "controls" menu every time to change the right stick to from normal to inverted and back. This issue won't go away until controllers are advanced enough to automatically detect who's holding them, but the Wii U GamePad makes it a bit easier in Black Ops 2 by having that option right on the touch screen.
So instead of pausing and navigating through the menus to change the stick inversion, you'll just tap the "controls" icon on the screen, then tab "inversion" to have it switch. You can also adjust sensitivity and a few other useful quickies here. It's very convenient.