If the iCade Mobile game accessory isn't your thing and you're a retro type, consider the GameDock, a cool new Kickstarter project which turns your iPhone into an old-school TV-based game console. It's simple, really: the GameDock, as the name suggests, is a game dock-like accessory where you plug your iPhone, iPad or iPod touch, akin to a game cartridge.
You can also pair your device with it over Bluetooth. It includes video output and comes equipped with an USB game controller with physical buttons and an HDMI adapter...