The Gnomish Army Knife is quite possibly one of the greatest creations for crafters and gatherers. It reduces over various profession-related items into one and is usable by non-engineers!
Can act as: Gyromatic Micro-Adjuster Arclight Spanner Flint and Tinder (which no longer needs simple wood to make fire) Blacksmithing Hammer Mining Pick Skinning Knife Jumper Cables (engineers only)
These knives are good for lvling engineering, so they should be cheap on the AH. Enjoy!