The high-rep squat and deadlifts are some of the most productive tools (with steroids and proper food intake being the others) at building muscle and general body strength. They should be the core exercises in the routines of anyone who's goal is to build muscle.
Clean and jerk and other olympic lifts are, in my opinion, excellent exercises as well but very few people know how to do them properly as very few trainers and coaches know how to teach them correctly.