Normal creatures disapears after a while so why not leave them in a rat you have killed somewhere?
This.
Kill any creature (or NPC even) and put all your useless items in that creature. After 72 game-hours away from that cell the creature is removed from game memory.
Perfect way to delete anything from the game.
This is the standard (and intelligent) way to keep your Save file nice and tidy.
Don't sell every useless cup/plate/ash yam/sword to a vendor, because the game will remember it forever. Instead, put it on a corpse of something you just killed. 72 hours later, it's erased from the game forever, which keeps your Save file smaller and cleaner.