How "unique" do you want and are you willing to scratch build ?

If you are willing to scratch build, and if need be do your own plans, there are several unique/different planes out there.

A few I can think of offhand are the Bellanca Airbus (Cleveland has plans), FW-56 (Stosser) [I have a short kit, plans and assembly manual] and REALLY unique/odd ball is the Transvia PL-12 Airtruk (remember the plane from Mad Max Beyond the Thunderdome ? ) At present, there is a gentleman in New Zealand that has plans for a 117" wingspan of this plane. Remember, plans can be reduced and enlarged.