When I installed Cairo-Dock because Docky kept crashing on me, I didn't like any of the default themes.
Looking at other third-party themes on the Web, they all seemed to have a circa-2003 vibe to them, which I didn't like either.
Several hours of tweaking later, I came up with CircleTab, which has been my dock theme ever since.
Instead of the standard fuzzy dot indicating an open window, CircleTab displays a slick-looking tab below the relevant icon.
Best results when used with the Numix Circle icon theme (as shown in the screenshots).
Hope y'all like this theme!