Closing A Revolver's Cylinder: We've all seen someone in a movie flipping a revolver's cylinder closed with a flick of the wrist. This works great on TV or in the movies but is horrible for the gun. You can break the cylinder stop or distort the yoke/crane when doing this.
It also makes you look like you have no idea what you're doing if you do this around people that know guns.
Shut the cylinder with your off hand and don't flip it closed.