Maybe a scythe for my witchdoctor. If they ever do come out with these types of weapons, they should probably be classified as exotic weapons considering you normally don't fight people with fishing poles or bowls of herring.
How about a floating, glowing crystal ball for witchdoctors? It would technically count as a 'staffy' weapon. It could shoot out lightning bolts or maybe ghostly spirits. If not a crystal ball, maybe a decorated juju skull, with the attacks coming out of the skull's mouth.
I have some new weapon ideas they could put in the black market. They could have throwing stars or blowdart guns. Some staffy weapons like a bone with some fingers of a staff with a lantern dangling from it. It would be fun to see the handheld cannons the threshers use to.
Anybody remember Super Mario RPG? Princess Peach had totally awesome fighting ability including the super large slap glove and the frying pan. She was so Privateer I would love to see things like that. Although you can get lead pipes from Red Fox's minions
Maybe that Musketeer weapon used in the Pirate101 Commercial could be put in. It seemed like it was launching sticky mines of some sort at the Sharks. I'm only guessing that they are mines because they look like the sticky mines that the Demoman uses in TF2. (I'm assuming they used it since they weren't allowed to have guns in a television trailer, but it was an interesting weapon nonetheless.)
It would be nice to know what world is coming out next so we can start our theories on what some weapons could look like.