What items are 100% totally useless when you have all DLC?
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?
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Do you need junk in Fallout New Vegas?
Some of them can be used to craft a few things, and things like pre-war apparel and cigarettes can be exchanged late for Sierra Madre chips. A few junk is needed for an unmarked quest if your repair skill is not high enough. But in general, in vanilla game, no, they are junk.What are misc items used for in Fallout New Vegas?
Misc items are not totally devoid of use. There are certain quests which require misc "junk" items, including Conductors. Various recipes also require these items. Notably, Tin Cans have use in a few quests (for one you need 100 pieces of junk metal... that's a lot of cans!) and in certain recipes.Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
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