Here they are in my totally biased opinion:
Exakta (has to be #1 as it's the pioneer)
Nikon F (mainly the F and F2 please, rock solid in all respects)
Canon (R, FL, FD bodies) (reliable, great lenses)
Pentax Spotmatic (and K1000, MX, LX) (top-drawer optics)
Praktina (all the rage behind the iron curtain, plus lots, and lots, of fine German glass for these babies)
Amateur systems deserving honorable mention: Konica, Topcon, Miranda (if she's working), Rollei SL35 (VSL1, etc.), Petri (cause of good looks only), Icarex (amazing quality)