I can think of three answers.
The Stellar type from Indigo Disc
The ??? Type from glitches, eggs, and the move Curse
And the Bird type from Missingno
You got it! It's crazy how most people don't even remember curse from back in gen two when it's type was ???
Fun fact about the ??? type:
The only pokemon that could use curse before it became a ghost type move were Gastly, Dugtrio, and Hitmonlee. (Going off of Pokemon Stadium 2.)
