All the lists I found include things like Coffee Mugs which aren't actually useless because you can give them to Muggy. I haven't found any lists that are up-to-date for all DLC.
What items can I definitely throw away? I.E. What items can't be used for crafting, can't be traded with NPCs for useful items, and aren't used in quests?
Best Answer
Here's the list of completely unusable items (which means they serve only decoration purpose - no crafting, quests, dialogues, nothing else). I'm not 100% sure the list is complete (maybe 99%) - there might be an error or two.
BASE
Bent tin canDEAD MONEY
HONEST HEARTS
OLD WORLD BLUES
LONESOME ROAD