Well, it's a tough one but I suppose multiple male herbivores (horned are best) are good because they bring out the fighting behaviour but whereas carnivores kill, herbs just walk away.
Enrichment is good too, try to make a big exhibit and put as many different enrichment items for that animal in as you can, then you'll see different behaviors (e.g. stuffed dummy for cats, seal dummy for sharks, dino prey dummy [if you have dd] for rhinos)
You could always go for natural exhibits and put in carns and herbs with no carn food but herb food. When they kill a herb, let them all eat from it then delete the remains and replace the herb. The best thing to do this with would be lions or wolves and herding animals, then you'd see herds behaving aggressively and carns hunting as a pack.
One I use all the time is this: Don't use an animal for ages, then when you do use it a while later, your interest will be rekindled. I haven't used the RTLemur for a few months so when I use it again it will be more interesting than something I use all the time.