Most RJ-45 connectors (without a boot on them)… The connector only fits one way, the orientation is clear on both ends while holding, looking or even by feel if you have to do it blind and it locks into place easily. Only issue is how fragile the locking part is, which boots are supposed to help protect but make more difficult to use.
I like reversible connectors like lighting and USB-C but I find them too small and fragile in general and they are not very satisfying to connect.
I have a special hate for connectors that are HARD to blind connect or even tell at a distance like USB-A, HDMI and Displayport which are ether rectangles or slightly not rectangles that are close enough that is hard to tell in the dark behind a device.
I have a strong dislike for connectors with thumb screws, but like locking connectors like Centronics or as noted RJ11 or RJ45.