On seomoz, Matthew Inman points to 15 rarely used CSS properties, and why you might want to be aware of if you don't already use them. I have to admit to only using a handful of these, and not with any regularity.

  1. clip
  2. visibility
  3. text-shadow
  4. content
  5. quotes
  6. counter-reset and counter-increment
  7. marks
  8. page-break-before and page-break-after
  9. orphans and widows
  10. font-size-adjust
  11. font-stretch
  12. font-variant
  13. caption-side
  14. table-layout
  15. empty-cells

http://www.seomoz.org/blog/css-properties-you-probably-never-use