The Pepper Palace in Gatlinburg, TN makes many of its own sauces (making it uniques as far as most hot sauce shops go). They have a sauce called "The World's Hottest Hot Sauce" that measures at about 1.2 million shu. I tried it, and it is undeniably scorching. In all honesty, though, once I get above a certain level in extract sauces, I can't tell the difference any more, other than to say OUCH!! That's hot!!!
BTW, they have a new sauce just released called "The Hottest Sauce in the Universe". I bought a bottle for my collection, but haven't tried it yet. I'll give it a shot my next trip to Gatlinburg.