I know its an easy one, but fuck it, its the only one that I have issues with off the top of my head that hasn't already been done to death. The Monster Hunter universe.
An ecology like that wouldn't have any chance of surviving for any length of time. Everyhing should be driving everything else to extinction. There are two or three species of herbivores, and then almost every other organism is an apex predator. And most of them are huge! Christ, there is a carnivore the size of a mountain in the game! They would eliminate the entire food source in a month!
Then there are the hunters. They can't take a smack from a wyvern's tail (reasonable enough) but they can happily throw themselves off the side of a mountain just to get to the bottom faster? Not to mention the fact that they can carry a metal sword that is significantly larger than themselves and swing it around like a sack of potatoes.And don't even get me started on the cats.