I found this interesting article in the BBC today about an octopus in Borneo that exhibits mimicry of certain fish. Researchers used a genetic analysis to study the behavior of the Indonesian Mimic Octopus (I know clever name, right?) What they found was that the octopus evolved the ability to mimic toxic fish, sea snakes, and other predators to help ward off its own.
Probably the most well known example of mimicry is in butterflies that exhibit the coloring or markings of other toxic species to keep themselves from being eaten by birds. Of course, I have an article about this: Genetic Hotspots Solve Mimicry Mystery from BioTechniques.