A few Wenger Swiss Army knives include a wrench. It is a unique tool that is not found on any Victorinox knives or Leatherman multi-tools (though some of the newer flat tools from Leatherman also include wrenches).
Uses: The Wenger wrench has a serrated slot that will grip hex nuts that are between 5mm and 9mm in size. It also works on hex nuts sized in inches (3/16" to 3/8"). The wrench grips well, but it is more likely to damage the nut than a regular box, open end or adjustable wrench.