Brachiation
Climbing, pulling, and swinging movements focus on large muscle groups, develop grip and forearm strength, and improve both external object and body control, and thus have broad functional application to other forms of exercise, work, and sport (rock and ice climbing are just two of the most obvious examples).
The kind of “lifting” involved in body-pulling movements such as rope climbing and pull-ups complements the hip- and trapezius-oriented pulling movements we do in the deadlift and Olympic lifts. The type of pulling required to pull the body against gravity or other resistance toward the hands—and in moving and lifting the body while hanging—engages different muscles in different ways, making the lats, posterior deltoids, chest, and biceps the prime movers.
For more, see the CrossFit Journal issue on macroclimbing from 2004.