Floating Clumps of Arrows
If the player (and possibly NPCs) has been shot with arrows, they stick in the player's body. If the player goes through a load door into an unloaded cell (one that hasn't just been visited), the game engine doesn't know where to put the arrows, so they are moved to co-ordinate 0,0,0. In some interior cells, this origin point is visible, and the clump of arrows can be seen there. They can't be picked up but can be selected with the console, and will fade away via the same game setting that they would fade from the player's or NPC's body.