Lenovo Show Arcade Laptop Casemod
This is quite the thing, via Technabob: it's a case in which to place a laptop, turning it into an arcade machine. The case hooks the laptop up to arcade-style control pad and buttons, while providing an extra slide-out keyboard beneath the main cabinet so that you can still use it as a PC. Frustratingly, this doesn't yet appear to be a commercial project, and instead is simply a demo project by this chap. As casemods go, this is both practical (if you're an arcade nerd) and awesome, and totally should be a commercial thing. There's a video of it being demonstrated in action beneath the click.