Do scissor switches count? TypeMatrix 2030, and I'd try to get higher-quality keycaps for it... somewhere. Otherwise, I'd like to try some programmable Cherry G86.
I don't really mind BTC 51xx (w/ Cherry MX-compatible keycaps), old KeyTronic, Dell QuietKey, Silitek MaxiSwitch and possibly some others, but the layout! There's no way I'm going back to full-size AND winkeyless AND staggered layout. Maybe MS Natural Elite or Goldtouch Adjustable Keyboard...