Add some steely elegance to your project with these Metal Ball Tactile Buttons. They've got a nice industrial shine to them along with a light blue underbelly. Not only do they look good, but they're also good if you have an actuator that will be pressing the button at an angle!
Little clicky switches are standard input "buttons" on electronic projects. These work best in a PCB but can be used on a solderless breadboard as shown in this tutorial. The pins are normally open (disconnected) and when the button is pressed they are momentarily closed.