1st choice when I need to be quick - Nikon F3 or FM3a.
1st choice when I have time to take separate meter readings - Leica M2.
1st choice for scientific work (photomicrosocpy, etc.) - Canon EOS5 with Nikon lenses, because the mirror-up function is so simple (one press raises mirror and fires shutter 2 sec, later).
1st choice for a change - a 1950s Voigtländer (Vitessa or Vito) or a screw-thread Leica with an old lens (Summar or Elmar).