A percussion massager. Yep. You know, those things you always see at Brookstone/Sharper Image and try out but never buy? Well, I have one (It was from Macy's, $40 I think). In addition to massaging my sore joints, it's the perfect e-liquid mixer! No need to stir things in a beaker and waste the residue. Just pump everything into a 30mL plastic bottle (probably won't work with glass), and let the massager do the work! There's a certain art to it... I hold the bottle by the cap... the outer cap is loose, but the inner seal is tight, so that literally allows for "wiggle room." with the right amount of pressure and the right angle of attack, you'll be all mixed up in about 60 seconds... [Cue the vibrator jokes] Really, it works if you happen to have one!