Same. Is it actually a contest for most obscure? I just figured it was a fun question as a requirement to enter. I put the Nokia-bot from the 2007 movie as my favorite.
Does it have to have a toy? If not, Raze. He was only featured in a Transformers anthology of short stories, forget what it was called. He turned into a jukebox, which was awesome.
head Maybe those animal headmaster Transformer that only had the stand alone toys unless they had a story in Japan.
As far as toys go, I'd say Car, Truck, and Jet. I'd never heard of those guys until I was poking around tfu.info one day, and that's still the only place I've really ever seen anything about them.
Not knowing much about the older, more obscure characters, I'll just go with the oldest toy in my collection, who gave me hell until I determined (here on TFW, go figure) that yes, he's an official Transformer. It's Triggercon Crankcase. I used to have Dog Fight, too, but lost him years ago...I think. Crankcase is obscure from a personal viewpoint, and the Triggerbots/cons in general were odd to me.