A few of the larger Swiss Army knives from Victorinox
include a combination shackle opener and marlin spike (or marlinspike).
This tool is useful when working with knots in heavy ropes, particularly when they are wet or have jammed tight. It's also useful for pulling rope strands apart in preparation for rope splicing, or for threading a new rope strand into the space between other strands.
Uses: To use the marlin spike, poke it between the rope strands,
and use it as a lever to pry apart the ropes or rope strands. Because
the blade has no sharp edges, it won't damage the rope. If you want
to thread a new strand into an existing rope, pass the new strand
through the hole near the tip, and shove the tip into the space between
two existing rope strands.
You can also use the tool as a shackle opener, or as a lever when working with any other type of unwieldy material.