And I would name ArchLinux. Apart from being a great distro (I don't compare it to OpenSuSE or Mandriva, but after trying Slackware, Gentoo or Debian I found Arch to be amazing. That's just my opinion anyway, so I don't want to cause any flame here although I'm ready to explain my point of view) it also has a great project - KDEmod
http://www.kdemod.ath.cx/
It actually features all the greatest customizations for KDE from all the distros. First, it has packages like kde-multimedia divided into singular applications like kde-multimedia-noatun, kde-multimedia-juk, etc. Just like gentoo, if I am not mistaken. That's really handy, because I personally don't really need all those default apps. The other thing is, for example the SuSE's kickoff menu. Looks nice, although I didn't think it to be more efficient than the default one apart from having an integrated beagle without all those GNOME dependencies.
The default theme differs greatly here - it is based on Domino widgets and Tango icons. A weird mix of Vista, Mac OS and Ubuntu, but anyway it's better than the default KDE 3.5. And there are many more nice customizations which make KDEmod a great stuff. That actually made me switch to KDE (I used to be a GNOME user). So, personally I am waiting for KDEmod's customizations for KDE4, although at first there would only package splitting which is however really nice.