Let's see if we can't refresh that rusty old memory of yours. Is she on SATAN'S RIDGE? Or NIGHTMARE CANYON? What do you think Joanna? Yeah that's it. Right smack dab in the MIDDLE, at CROC FALLS!
The Wicked Queen in Snow White and the Seven Dwarfs is the first in that canon and a particularly wonderfully nightmarish example. (This may have a lot to do with her being voiced by Lucille LaVerne, a stage and silent film actress. She's also visually based on Kate Hepburn.)
Actually, although she has a few drips of ham, the Queen is one of the more subtle villains out there. When she turns herself into the hag on the other hand, all bets are off, and she chews the scenery wonderfully.
Whenever Beast gets angry, he hams up accordingly ("Then go ahead and STAAAAAAAAAAAAARVE!").
Except maybe Pat Carroll's Ursula the Sea-Witch from The Little Mermaid, who actually turns herself into a very large...octopus...for the finale. She may be the first and only Disney villain to actually shake her moneymakers for the camera.
Even better, in the second film he gets a whole musical number, every line of which seems to made entirely of pun-filled ham.
The only thing that could make Jafar more hammy is if he was voiced by Tim Curry. Case in point; his Reprise of the Prince Ali song.
Jafar may have been killed off by the start of the TV series, but the Hamjitsu was conserved by the late Jonathan Brandis as the smarmy sorcerer Mozenrath. Who knew you could fit all that ham into a pair of leather pants?
From the TV series, Mechanicles, "THE GREATEST OF THE GREAT GREEK GENIUSES!"
Besides Zurg, the Toy Story series has Jessie ("YEE-HAAAAAWWWW!") and an obvious one in Hamm the piggy bank ("PIG PILE!"). Buzz dabbles in it sometimes, especially in Toy Story 3 when he's reset and starts speaking in Spanish.
Bolt has both Bolt the dog and Rhino the hamster as somewhat hammy characters, but the director of the Show Within a Show as easily the hammiest character in the movie.
The Director: Let me ask you, Mindy from the network, what do you see here? Mindy Parker: Uhh... the dog? The Director: "The dog" she says. Oh, Mindy. Poor, poor Mindy. Mindy Parker: ... am I missing something? The Director: You're missing everything, Mindy. You see a dog. I see an animal that believes, with every fiber of his being; EVERY FIBER; that the girl he loves is in mortal danger! I see a depth of emotion on the face of that canine, the likes of which has never been captured on screen before. NEVER, Mindy from the network. We jump through hoops to make sure Bolt believes everything is real. It's why we don't miss marks. It's why we don't reshoot. It's CERTAINLY why we do NOT allow the dog to see BOOM MIKES... because, Mindy from the network... if "the dog" believes it... then "the audience" believes it.
Anna from Frozen is probably the hammiest princess in Disney history.
Television and shorts
The title character from Darkwing Duck, particularly when he's monologing. Over on the villain side, we have Negaduck (whose hammy nature is befitting, as he's DW's Evil Twin), and Tuskerninni, an ex-actor/director turned criminal:
Darkwing: I caught that hateful, underhanded ham Tuskerninni robbing a bank!