The Klemheist knot is an alternative to the Prusik knot, useful when the climber is short of cord but has plenty of webbing.
The Prusik is a knot used for mainly for emergency use. Some carry between one to three cords specifically for it quickly if needed. One can be used to quickly secure persons's position to correct problems with equipment, two can be used as a method of ascending a rope.
The Figure-of-eight loop is considered strong and secure. Can be tied by taking a bite of rope and tying a figure-of-eight knot or can be tied directly around/through objects before weaving back through the first figure eight knot(Figure-of-eight follow through).
The Stevedore knot is tied at the end of a rope to prevent the end from unraveling, slipping through another knot, or passing back through a hole, block, or belay/rappel device. It is more bulky and less prone to jamming than the closely related figure-of-eight knot.