I find this MoMA World Clock simply brilliant in design and effectiveness. Perhaps it's my many years of engineering education (heh - it's more like my many more years of video game playing), but looking at this one clock I can easily read the time in other cities by quickly performing the rotation to align the "12-o'clock" appropriately.

While their Barrel Clock is neat too, the names of the side of the barrel make the single look, lots of info paradigm not work.

(via RedFerret Journal)