The key bulge. That tangle of metal in your pocket that does no one any favors, and is usually more hassle than its worth...until you're out and you actually need that key you almost left at home.
Instructable-r Stuartcom came up with this clever solution: hack a flip-out bike multitool to house your keys with a much more efficient packing ratio than the standard ring. Plus, Stuart only looks to be 15-years-old. It's awesome to see such creativity and DIY ingenuity at such a young age. We love it.
Get the full how-to at Instructables: Bike tool key set (MOD)