One thing that drives me NUTS are the items that you can only pick up by the base (the bust of the Gray Fox, bug jars, etc.). It's frickin' IMPOSSIBLE to display them properly in your homes. I end up trying to flip and fling them into place, get pissed off, and say "Fine, you're staying in that corner over there." And then I just have a random corner with a pile of bug jars and various objects, because screw that, man.
Skooma, books, notes(letters of assassination[ordered to kill me], diary entries, etc.), and keys
I collect mainly daedra hearts but I do collect bear claws, sabre cat teeth, antlers, bear tusk, and salt piles.
I have 27 daedra hearts. I find them in new places sometimes or wait for them to respsawn in places I know they can be found.
Like Jorvasskr and castle volkhier. Or I collect a heart from a daedra I kill.