Most un-loved material in SK crafting

So we all know that certain materials have a higher demand than others, like nobody's going to cry over picking a piece of warp dust or a trojan horseshoe. On the other hand, there's materials whose high abundance drives down prices on the AH but which are still required to craft highly popular gear, like Gel Drops, Ecto Drops and Scrap metal.
But what of unloved materials? Ones which are relegated to only crafting the crap gear that nobody wants? For the sake of this discussion we'll exclude the Zee Core since it has its own novelty value.
My nominations: Toxic Core, Cooling Cell, Fuel Canister, Power Cell, Waste Module, Nightshade

It's used in the Ionized Salt Bomb and Cautery Sword, the bomb and sword of regret.

Rocky Cores and Brute Cores. Nobody ever seems to buy them.
Well it's not that people don't buy them because they are unpopular, it's because everyone does jelly runs and has tons of them.
I'd say royal cores and reaper ribs are the most unloved.

Rocket Sprockets...buh I don't even bother trying to sell them.

Reaper Ribs, Flame Souls and -surprisingly- Royal Cores. Every FSC farmer has a ton of those already.
Send me all your Cooling Cell, Fuel Canister, and Power Cell plox.They're used in alchemers, which I'm kinda rage-crafting, if making two a day counts. 8|
As for unloved mats, I have no idea, actually. I don't notice mat drops too much...