1N4007 Rectifier Diode
When dealing with motors or other inductive loads, you need to be ready for a BIG back-EMF voltage spike when you power them off. If you don't, you'll be feed an huge voltage into your control electronics, most likely killing them!
That's why rectification diodes like the 1N4007 are inexpensive and popular protection devices. A set of 4 of these properly installed on motor control leads will safely snub out up to 1000V and 1A of current to your ground and Vcc power lines.
These DO-41 form-factor diodes are a bit bigger than standard 1/4W resistors, measuring ~5mm long (0.2") by 2.5mm (.098") diameter.