After coaching a group training session, Jamil and I maxed out on chin-ups. We tied at 18-each. 20 chin-ups here we come.
If you want an exercise that is incredible for shoulder flexibility and range of motion, strengthening the arms, core, and back muscles, as well as a true test of relative body strength, the chin up is your answer. Just make sure you extend all the way down and pull yourself all the way up.