http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation

I always find this amazing. Using a localised magnetic field to suppress activity in certain parts of the brain. What I find incredible is that it does work on a basic level, at least in terms of affecting people's performance on specific tasks when it is 'aimed' at a certain brain region (the stuff about repeated use curing depression and that sounds a bit.. snakeoily).

I want a portable version that I can shoot people with to make them temporarily drooling and slack-jawed.