I've always found that the Jamo Concert 8 and Concert 11 speakers, for being a conventional box, have a striking appearance thanks to the roundover profiles and the contrast of the front baffle to the main enclosure and the drivers themselves.
I'm also a big fan of the Wilson designs:
Sasha:
An older Watt/Puppy:
Among my absolute favorites in appearance are the B&W 800 series and the Sonus Faber Cremona series, but these have already been posted.