The folks at Arduino seem to be stepping up their game. With the new Arduino Leonardo board able to emulate USB keyboards and mice right out of the box, it seems the perfect time for Arduino designers to come up with a proper video game controller. This new board is called the Arduino Esplora and packs enough buttons and sensors inside to capture just about any user input you can imagine.
On board the Esplora is the same ATMega 32U4 microcontroller found in the newest Arduino boards. For input, the designers included an analog joystick, four tact switches, a linear pot, a microphone, and light sensor. The Esplora also includes a three-axis accelerometer, RGB LED, buzzer, and a breakout for an SPI-controlled TFT LCD display, lest you would want to recreate something like the new Wii U controller on your own.
You can check out everything the Esplora can do over on the official Arduino site for the Esplora library.