I bought an 12V vibration motor from China off of eBay (http://www.ebay.co.uk/itm/291580254219), originally to see if it could help tamp down the loose ballast on my layout modules before fixing with glue.
The motor, even on a 9V battery, vibrated the board so much that all the ballast soon was one stone thick in a layer several inches wide!
Well at £3.97 inclusive of postage it was not a big loss.
Then today I wondered if it could help me mix paint! I wanted to thin down some tube acrylic paint for use in my airbrush.
I mixed the paint 50/50 with thinners in a disposable plastic bottle and fastened it to the vibrator with an elastic band.
Result? A nice creamy paint mix!