I don't have a clue who Harold Hill is, but none of the characters I listed are very hammy. I guess you could make an argument for Gilda and the Dogs (that sounds like a band name) since they're pretty LOUD but LOUDNESS does not equal hamminess. Or maybe I just have high standards for Hams.
I don't count singing. If you count singing than every one of the Mane 6 is a Ham.
@ David: I kept Diamond Tiara on the Ham list because of her J. Jonah Jameson aspirations in Ponyville Confidential.
Pronounced "Sid-zellia"
What are you looking at?
The only time I'd call Fluttershy a ham is when she's been Discorded or Iron Willed.
Pronounced "Sid-zellia"
What are you looking at?
@Syd: Hmm, yeah. One saucy fanartist Pyruvate is doing a fancomic right now involving Dashie and the Spa Twins.
Diamond Tiara is a part-time ham. And for a while, she was also the big cheese.
Look at me still talking, when there's SCIENCE to do!
I think it was more she's a classic Umbridge type and soon as she got a little bit of power it went to her head. Whe's do that no matter what position it was, long as she had power over somepony.
Build a fool proof system, and the world will create a better fool.
My random thoughts