I have always been in favor of "luxury" tax structure for consumer goods. Food and other necessities should carry no tax, including on utilities, which is still bizarre to me that they get taxed, and then a sliding scale as as products become more expensive. If you buy a car, let's say, and you can only afford a used Corolla you would pay a lower percentage than someone buying, say, a brand new lexus. Of course there is already a form of luxury tax on high end automobiles but I could support a sliding scale that didn't just kick in at a single purchase of $100k or whatever.
I prefer the flat tax idea with no progressive scales at all. Everyone has an interest in cutting guv spending. Everyone should have a reason to vote for less guv.