Well, the Sesame Street Unpaved book refers to Roosevelt Franklin as an "Anything Muppet", so maybe Guy Smiley could be considered one too.
On the other hand, they have a specific page for "Anything Muppets" that show the more obscure characters like the Rhymies, the band members of the Monotones (without Little Jerry) and unnamed characters like the doctor and patient in "Ten Commandments of Health."
Technically, any muppet that gets used as different characters with different facial parts could probably be considered an "Anything Muppet". Characters who could never be considered Anything Muppets would probably be Ernie, Bert, Big Bird, Oscar, Kermit, most of the monsters, etc. JMO