One of the most interesting languages I have worked with in Papua New Guinea is Rabaul Creole German, which its speakers call Unserdeutsch ("Our German"). The language arose at the end of the nineteenth century in German New Guinea when Catholic missionaries at Vunapope, near Rabaul in what we now call East New Britain established an orphanage for mixed-race children. The education at the mission was all in Standard German, but the children played with the language, using German words to make sentences based on the early form of Tok Pisin (New Guinea Pidgin English) used as a common language in the German colony.
As these children became adults and married each other, this new language became the mother tongue of their children in many families. For several generations, and even after the Australian conquest of the German colony in WWI, it was one of the main languages of the small multilingual mixed-race community centered around Vunapope and Kokopo (formerly called Herbertshöhe). When most of the community dispersed and emigrated to Australia with Papua New Guinean independence in 1975, the language ceased to be learned by a new generation of speakers. Today only a few dozen speakers remain, the youngest in their sixties. It is perhaps the only language of Papua New Guinea to face extinction through emigration. It is also the only known example of a creole language based on German.
Friedel Martin Frowein, a German linguist and doctoral student in Australia, has made a website where a number of articles and recordings about the language can be accessed: http://www.uni-koeln.de/gbs/unserdeutsch/index.html