Yeah, Richard did a really good job on some of the sketches with the Beetles - he sounds really authentic. Those are some of my favorite Richard moments on SST - and of course, I do like Placido Flamingo and Don Music as well. (The outtakes from the Declaration of Independence sketch really crack me up.)
Like I said, Scooter heads the list of my favorite Richard Hunt characters, both on TMS and in general, and I also like Beaker, Janice, Statler and Sweetums.
On Fraggle Rock, I like Gunge and Junior, of course, but I love some of his minor and one-shot characters as well, like Gillis, Beige, Turbo and the Spiderfly.