What is something similar to a mini massager?

(please don't answer this question innapropiately) I need something that vibrates or moves a lot. I am trying to simulate an earthquake and I thought a mini massager could work, any other ideas?|||Any sort of motor that is out of balance will work. I suggest getting a really cheap electric drill. You can put large bolt in the chuck. Bend the bolt first. When you turn it on it will vibrate (wobble). If the drill is a variable speed drill you can change the vibration rate. Attach the drill firmly to the model you are making.