If Macgyver carried a fish around in his pocket, we feel fairly certain that it would be a Lil Guppie multi tool. The versatile pocket tool has an impressive amount of features for its small 3" size.
The multi-tool features an adjustable wrench that opens to 10 mm, a built in carabineer so you can clip it anywhere that you find convenient, and a razor sharp stainless steel blade which allows for one hand opening and closing.
Of course a multi tool would not be a multi tool without a couple screwdrivers made into the unit, and the Guppie has a flat blade screwdriver built into its tail and a Phillips screwdriver that extends from the body.
The handy Lil Guppie costs $19.99, and you can find it at ThinkGeek.