Somaliland, an unrecognized state in the Horn of Africa, after achieving independence from Somalia in 1990, has enjoyed a thriving multi-party democracy with peaceful transfers of power between leaders.
An interesting quirk of the Somalilander political system is that the constitution only allows 3 political parties, currently Kulmiye, Kaah, and Waddani. The original 3 were chosen for their broad political appeal, and when the former parties UDUB and UCID became unpopular, they were replaced in special elections.
In the 1969 Somalian(not Somalilander) parliamentary election, 27 different parties won seats, with the vast majority being small parties generally oriented around clan interests.