The Scorpion!
It's why Northrop was never really able to sell a first line combat aircraft to the US military for a long time -- the Scorpion series left a pretty bad taste in a lot of people's mouths.
While a lot of aircraft in the fifties had flaws, and "no go areas" -- the F-100 series had a particular part of it's envelope which was basically very dangerous -- the Scorpion was unique for having flaws which could kill the pilot even if he was very conscientious -- like the wings falling off in flight (and when that was fixed, then the engines would explode in flight).
Despite these flaws, I do like the Scorpion -- mostly for the cavalcade of errors which kept cropping up.