The WM-747 Ripper is an industrial saw that can shred through just about anything. Its rounds are actually small radial blades that shoot out and then spin at a distance. After firing off a round, the blade will spin at a distance as if connected by a tether. You can then direct the blade by aiming your Ripper wherever you want it to go.
The secondary function fires a single blade as a projectile that can slice through multiple enemies. Both the primary and secondary functions of the Ripper use one unit of ammo.
One major warning about carrying this weapon is that "random" ammo drops have a tendency to gravitate towards this weapon disproportionately. For example, if you are carrying a Contact Beam and an un-upgraded ripper, you will find your inventory will generally fill up with too much ripper ammo - leaving you without ammunition for the Contact Beam. Unless you plan on using the ripper as your primary weapon, leave it in the safe.