Nintendo's new adapter that allows classic GameCube controllers to connect to the Wii U has a new use now that a programmer going by the name "elmassivo" has developed an open source driver that allows a Windows PC to recognize the USB adapter and accept GameCube controller input.  Now you can use authentic Nintendo hardware to play your favorite PC games.  I haven't tried it for myself (so use at your own risk), but I'm glad to see that exists.  Here's some of the README file:

This is a vjoy feeder application written in C# using LibUsbDotNet.

It allows for communication with the WUP-028 model of the Wii U to Gamecube USB adapter.

This driver has been confirmed to work on Windows 7 and Windows 8 so far.

For reference:

• Z-Axis is the L trigger

• X-rotation is the C-stick X axis

• Y-Rotation is the C-stick Y axis

• Z-rotation is the R trigger

• When calibrating the triggers, do not make them click (hit the button), it will cause you to go to the next screen and could mess up your calibration.

• Rumble is not currently supported.

• Input lag is variable as of the 2014-11-28.5 release. It defaults to 10ms (~2/3 a frame) and can go as low as 5ms (roughly 1/3 frame) or as high as 30ms (just under 2 frames). Faster refresh rates (lower values) will use more processing power but be more responsive.

Now you can use a GameCube controller to play Windows versions of classic GameCube games like Resident Evil 4 the way they were meant to be played.  I love how the community steps up to fill needs left open by the original hardware producers.  I've given my DualShock 4 controller a second role to fill by connecting it to my PC and it's become my primary Steam gaming controller.  Find a need a fill it, I say.