I've actually found a few things potentially useful, and tempting. Hair clippers (for my dog), crockpot, mitre box. But it skeeves me to even think about touching most of what I find...food, dishes, clothes, coins, cigarette butts, unopened mail, yep, litter boxes too. Even the skeletal remains of a dog (at least, I think it was a dog...not much left but the hair and poop on the floor).
Worst I've seen in an actively-marketed REO...the toilet bowl with about 10 dead mice in it.