I suppose the other really obscure G1 Hasbro Cartoon Decepticon Characters would be Wingspan & Pounce as I think they were only in one episode as well. Scorponok was in two though he only appeared briefly at the end of one of those.
If we are talking obscurity are there any other Decepticon Characters that were in two episodes or less? So far we have:
Overkill
Slugfest
Runamuck
Runabout
Pounce
Wingpan
Scorponok
I can't think of any myself. Even the Headmaster and Targetmasters were in 3, though not sure their partners were. Reflector is definetly obscure but was in quite a few ep's and the movie. Octane was in a few if you count 5 Faces of Darkness. The Terrorcons were in at least 3 I can think of off the top of my head.