Well all fish are individuals, therefore they are all unique :D. Since that's probably not what you meant, there are a few fish that are quite rare in the hobby - either because they are from remote places, are difficult to collect or have some kind of aberration. Unfortunately, these are usually expensive. I've coveted a tigerpyge (sp?) angel for years, but they are very rare and I never end up being willing to fork over the $$$. Keeping groups of fish is something that most people do not do, so that seems to me to be unusual; beyond that, it's the usual fare.