"Palace" (Abu Dhabi), from the Colnect catalog
"Costume of Motalskiy region" (Belarus), from the Colnect catalog
"New model of electric locomotive" (Georgia), from the Colnect catalog
Right now the catalog has many detailed sub-categories: Countries, Emissions, Formats, Printings, Perforations, Colours, Years, Face Values, Currencies, Themes and Catalogs.
"Peaceful Visions" (UNO New York), from the Colnect catalog
The first perforated stamps, though, saw the light of the world in 1854 in Great Britain too. In the next years other countries issued their own perforated stamps.
"Nordic Food Culture" (Denmark), from the Colnect catalog
Another unique stamp is the Banana stamp issued in Tonga! :)
And finally, if you want to contribute to stamps catalog, follow the instructions here.