At the animal shelter we have a "shelter dog," a Golden Retreiver that we decided to keep for ourselves. His name is Rufus, and he's a great dog, still a little young (read: excitable at times), but very quick to learn and very friendly. He would play "fetch" for hours if you let him, and loves everyone.
Rufus was intrigued by a rabbit we got in. The rabbit was mildly interested in him in return, and not at all afraid.
They got along for a short while, until the rabbit decided to try an experiment and see if breaking into a run would trigger an instinctive chase-reaction from Rufus. The experiment was a total success, much to the rabbit's surprise, and it was spared a potentially-traumatizing conclusion by me tackling Rufus as he ran past the third time.