One of the most important resources in the world in the modern era has been oil, but arguably at no time more than during WW2 where many of the Axis' plans revolved around the procurement of a steady supply of the black stuff.
The main known locations for oil in the early 20th century were Texas, Venezuela, the Caucuses, and Indonesia. Venezuela was easily blockaded against Axis interests, and Nazi Germany and the Empire of Japan made grossly over-ambitious plans to conquer the Caucuses and Indonesia respectively to supply their war machines. When we see stories involving alternate outcomes to WW2, it generally involves these plans somehow working out for the Axis.
However, it is one of the ironies of history that little did the Axis realise that had actually had been sitting on one of the world's largest deposits of oil in the world in Italian Libya. Today Libya clocks in at 48,363 million barrels of reserves.
Taking into account the historical constraints that existed at the time, what different course could the world have taken had Mussolini found this vital resource in 1937 in his own back yard?