Of hazelnut's most recent list, I'd vote for including relics, spirits, science samples (I wasn't sure if they were worth anything), and wildflowers, and maybe stolen objects.
As for some of the others, I can't see one person accumulating enough LTHP for 4 rewards, and on medium lifespan, no one person will get 4 of the after-school and field trip stuff. As for handiness upgrades, you have to buy the objects to be upgraded.
But it does look like we'll need an official list.