Bowline on a Bight
The Bowline on a Bight is a knot which makes a pair of fixed size loops in the middle or at the end of a rope / line. The loops create to holds, handles to tug on, etc.
It's advantages are that it's loops do not slip and it is reasonably easy to untie after being exposed to strain.
It is a strong knot that can be used in overboard rescue, towing, and even to make an emergency Bowswain's Chair.