Which African country was never colonised, apart from a five-year Italian occupation?

Ethiopia. Italy invaded in 1895 and lost at Adwa in 1896 to Menelik II's army - a defeat of a European power by an African state on an open battlefield, which was not supposed to be possible and which secured Ethiopian sovereignty through the entire scramble for Africa.

It was not luck. Menelik had spent years importing modern rifles and artillery from several European suppliers, playing them against one another, and he fielded something like 100,000 men against a much smaller Italian force operating on bad maps and worse intelligence. The war began over a translation: the Treaty of Wichale said one thing in Amharic and another in Italian, with the Italian version making Ethiopia a protectorate.

Mussolini came back in 1935 with aircraft and mustard gas, in violation of treaties Italy had signed, and the League of Nations did nothing meaningful - Haile Selassie's speech to it in Geneva is one of the documents usually cited in the League's obituary. The occupation lasted five years and was never a colonial administration in the full sense. Adwa's significance outside Ethiopia was enormous: it became a reference point for anti-colonial and pan-African movements for the next sixty years.