Scrapper has something approaching a seat shape moulded around the screw-hole under his canopy, so if you count that I suppose he's the first Decepticon with one.
"I used to think it was a terrible thing that life was so unfair. Then I thought, 'what if life were fair, and all of the terrible things that happen to us came because we really deserved them?' Now I take great comfort in the general unfairness and hostility of the universe." — Marcus Cole, Babylon 5 — A Late Delivery from Avalon