Whenever I leave home, I wear a multi-tool on my belt. It's a Winchester-branded knockoff of a Leatherman PST that I find myself using on a daily basis. Like many classic multi-tool designs, it's based on a pair of pliers.
Pliers are handy. But Instructables member M3G finds that hammers are, too, and converted an old hammer into a multi-tool.
His modified hammer is a bottle opener, screw driver, ruler, and nail holder. The bottle opener is a simple nail driven in at the optimal place on the hammer head. The screwdriver is a reversible bit holder held in place with a magnet glued inside the shaft. The nail holder is circular magnet glued onto the head.
Although it may not be practical for everyday carry, this hammer multi-tool could be a great item to keep nearby whenever engaging in crafting projects. You never know when you will suddenly need a particular basic tool or be able to put one to advantageous use--if only have it were within arm's reach. I always keep my multi-tool in my pocket while doing carpentry for this reason, even if I though I have all of my multi-tool's functions duplicated in single-purpose tools.