A good multitool packs a number of tools into a small device that's easy to carry with you. This DIY multi-key takes that idea and expands it to carry your keys as well.
Instructables user RobbGodshaw has instructions for a great DIY multi-key. His gadget includes several of his keys, as well as a USB flash drive, bottle opener, Phillips screwdriver and two Allen keys. The tight-fitting design ensures ease of access and low noise. Hit up the post at Instructables to see how he made it.
Multi key + Bike Tools + USB Drive + Bottle opener + Screwdriver [Instructables]