DB13W3

I'd like to nominate DB13W3 for Most Cursed Connector. I mean, just look at that thing!

Alt

Cable with 'male' DB13W3 connector, featuring a D-sub body containing three analogue RGB connectors but with a gap between the second and third into which 10 regular D-sub style pins have been sandwiched in two rows of five).

Bonus: there were at least two different, incompatible, pinout "standards" for this thing, so there was no guarantee that a random monitor with this cable would connect to your workstation, even if it had the right port.