A pictus cat or a rainbow are potential food items. I've seen oscars suck down on kitties even with those nasty barbs they have. The rainbow sharks are nice and narrow...easy to swallow. A better catfish would be one that is bigger than the oscar's mouth and will stay bigger than the oscar's mouth. Synodontis cats are ideal. So are leopard cats, channel cats, black lancer cats and plecos. Rafael cats, though don't get really big like the others I mentioned, they are really spikey. They'd be able to hurt an oscar biting down on them. Though you still want to get one bigger than the oscars mouth to start off. An oscar can get hurt messing with some kitties whether they succeed in eating them or not. Keep in mind, the catfish that are compatable with oscars do get really big and a very big tank would be needed to house the adult animals.
BTW...I like your list of "critters"...mine are:
1 son
3 cornsnakes (somewhat intended breeders)
2 ratsnakes (intended breeders)
2 australian frilled lizards (intended breeders)
1 water dragon (rescue)
4 white's tree frogs (rescue)
1 sulcata tortoise
1 rat
1 spiny hamster
3 cats
1 dog
1 brazilian red leg tarantula
1 goliath bird eater tarantula
1 red baboon tarantula
1 pink toe tarantula
1 columbian giant red leg tarantula
4 bettas
2 reef tanks (one at work and one at home)
Isn't life such a zoo???
LOL!! I use to have ferrets when I lived in Jersey. I miss them sooooooooo much.