Some states paid tribute for possessions that were legally bound to the Ottoman Empire but not possessed by the Ottomans such as the Habsburgs for parts of Royal Hungary or Venice for Zante.
There were also secondary vassals such as the Nogai Horde and the Circassians who were (at least nominally) vassals of the khans of Crimea, or some Berbers and Arabs who paid tribute to the North African beylerbeyis, who were in turn Ottoman vassals themselves.