As with humans, great Apes and bears amongst others it has been found the dolphins will usually prefer to use one flipper rather than the other.
It is also been found that with with dolphins as with humans right handed it is more common, only with dolphins this is even more extreme. Left flipper dolphins appear to be relatively rare.
Grey whales and humpback whales have both been shown to to favour one rather than the other side, so we may find that being left or right handed is more common throughout the Natural World than once thought.