I've got two, and there's no particular priority in which I ride them (primary/backup):

1977 Schwinn LeTour II, 2x1 drivetrain (The FD works, the RD is just a tensioner for a 16T freewheel).



1992 Trek 8000 MTB. 1x7 drivetrain, SRAM twist-grip shifter controlling a Shimano RD (hasn't blown up yet!).