A little buzzing motor, for any haptic feedback project. These vibe motors are tiny discs, completely sealed up so they're easy to use and embed.
Two wires are used to control/power the vibe. Simply provide power from a battery or microcontroller pin (red is positive, blue is negative) and it will buzz away. Works from 2V up to 5V, higher voltages result in more current draw but also a stronger vibration. Recommended voltage of operation is 3V
If you want to reduce the current draw/strength (for example, to control it directly from an Arduino pin) try putting a resistor (100 to 1000 ohms) in series.
Specifications
Tutorials