Most Dangerous Chemical?

This is one of the pretty standard questions that I'm guessing most every chemistry or chemistry teacher gets both used to and tired of answering.

I can say that my most dangerous chemical ever handled was dimethyl sulfoxide (DMSO) - which doesn't come any where close to being nearly as dangerous as the stuff discussed in this video.

I totally have a new respect for SO₃, a compound that I've written and of which I've drawn the bonding probably a few hundred times over the year. Turns out to be pretty nasty stuff.