A pocket rocket is a 4-inch-long vibrator sold by finer sex toy retailers out there (especially Toys in Babeland). It uses one AA battery, and it's quite powerful (and quite right) for the sensitive parts of your body, be it the tip of the penis or the clitoris; indeed its reputation as a clitoral stimulation device is very high. The Hello Kitty Vibrator is based on this model, as is the waterproof "Waterdancer" model.