Check out this muscle-up.  The gymnast is Andreas Aguilar at the 1991 World Professional Gymnastics Championships.  Andreas makes it look so smooth and easy, it’s truly unreal.  The rest of his routine is also great, including the unusual dismount, but a muscle-up like the one at the beginning of the video would take an incredible amount of strength.  I can’t even imagine how much training would be needed to build up the strength to pull so smoothly.  The cheering crowd in the background seems to agree.