This is a story about a small band of brave rabbits who, due to a horrible premonition by the runty yet psychic Fiver, decide to leave their warren and start a new life elsewhere. I hate quoting Wikipedia, but they summed it up well: Although the animals in the story live in their natural environment, they are anthropomorphised, possessing their own culture, language(Lapine), proverbs, poetry, and mythology. It feels more like an epic fantasy tale, where the hobbits and elves and orcs are transposed into rabbits and birds and dogs. While the subjects may be soft and cuddly, the actions of these bunnies are not. This is a story of life and death, of greed and cruelty, and of brotherhood and honor. This is not a cartoon for little kids; these rabbits are fighting for their survival, often literally. If you'll forgive the out of date animation, you'll certainly enjoy the story.
The Secret of NIMH
Magic, wizards, sword fights, betrayal, mutant rats! What more does a story need? The Secret of NIMH is the story of Mrs. Brisby, a widowed field mouse, and the rats of NIMH, a group of escaped lab rats with increased intelligence. The rats have mastered both technology and magic, but there is strife within their numbers. The secret to their survival just might lie in the tiny paws of Mrs. Brisby. While it's little more cartoony than Watership Down (the graphic rodent violence is kept to a minimum), it's every bit as enjoyable.
Legend of the Guardians
Legends of the Guardians takes things into a whole new level. While the first two movies on my list take place in our own world where animals live alongside people, Legends of the Guardians is set in some owl-based alternate universe. The plot isn't as satisfying as the other two, but the animation is nothing short of stunning. If you love looking at owls, then you'll love looking at jaw-droppingly rendered owls as they soar through a gorgeous fantasy land. Rich with their own culture and legends, these owls are badass warriors if need be -- they put on owl armor, and attach fearsome spurs to their talons so they can slice each other to ribbons in the air. Owls. Sword fighting. In the air.