Well, not me, but this website (much to the relief of millions). To support the First annual CSS naked day, this website along with thousands of others will have no stylesheet on April the 5th. The day is aiming to promote web standards and good semantic markup; something that all websites should have so, especially to allow people with disabilities to use your website.
I’m confident that my site will still work fine, but it’ll just be a little ugly. You can see how any website on the internet looks without stylesheets by using the ‘Web Developers’ toolbar in Firefox, or switching from ‘Author Mode’ to ‘User mode’ in Opera.