Hammers are one of the more versatile tools, but they sure do waste space, don't they? An enterprising Instructables user decided to make his hammer work harder by adding a screwdriver, ruler, magnet and even a bottle opener to it. If you've got the time, you can whip a similar one up.
Photos by M3G
User M3G has a step-by-step guide up on Instructables explaining the build process. It's actually a straight-forward design, requiring only basic tools such as a saw, drill and tape measure. The most complex part (and that's saying a lot) is collecting all the pieces you need.
There's some flexibility in how you go about it -- swapping the Philips head for a flat head, or adding some additional markings to the ruler -- it's completely up to you.
Just don't forget you can still use it to put nails in things.
The Ultimate Hammer (Hammer + Screwdriver, Bottle Opener, Nail Holder, and Ruler) [Instructables, via MAKE]