I was looking through my G1 figures and having watched most episodes here recently, were Pipes, Swerve or Tailgate in any episodes?
I can tell you at least that Swerve was in Five Faces of Darkness. I forget which part, but it was when he and the other minibots were trying to mess with Trypticon.
Pipes was also in FFOD. He's who lead the minibots (Warpath, Powerglide, Outback, etc.) when trying to defend Teletran-1 from Trypticon.
Pipes also appeared in Forever is a Long Time Coming. Off the top of my head, here's some characters that were never in the US show but had toys: Whirl Roadbuster Topspin Twin Twist the Omnibots the Powerdashers the Micromasters the Pretenders Junior Headmasters Junior Targetmasters the Duocons* Squawktalk Beastbox Grandslam Raindance Quickswitch ...quite a few more I believe, but it's early for me and my brain isn't working yet as I just got up. [* Duocon Flywheels did appear in the Season 4 intro.]
Hubcap was never in FFoD, or anywhere else in the G1 cartoon - but he may have (unintentionally) cropped up for a single frame in the movie - where a yellow Cliffjumper is shown in the acid cauldron scene. (See http://en.wikipedia.org/wiki/Hubcap_%28Transformers%29) It's certainly a theory that I like.
Anything after 1987 didn't appear in the cartoon. Buzzsaw was not in the cartoon all that much, Skids was in one or two episodes,
Yeah, I was surprised to see Swerve in that epsiode too...and I believe we knew saw him again despite the cartoon showing that he was alive after Trypticon's attack. Somehow I got the impression that Pipes was the most popular minibot in Season 3.
He was, for sure... I bet he got more airtime than any other minibot (except for Outback and Wheelie).