If we're naming obscure systems, I cast all my votes for "Dark Continent" a game of Victorian exploration and exploitation in Darkest Africa. Great White Hunters, Jungle Lords and frenzied Explorers brave malaria, hardships and forgotten magic in the quest for fame and glory.
Originally it may have been thought up as a Cthulhu supplement but then it became its' own beast and is a joy to play. Here is an audio game (the first of 12 I think) from Yog-sothoth:
http://www.yog-sothoth.com/docs2/av-dark-continent-01.mp3 sadly you have to become a patron to get the rest but well worth it.