Nigeria Depends on the area you consider as 'West Africa'. Mauritania is marginally bigger than Nigeria, and if you are prepared to consider non-coastal countries, Mali is even bigger. Look at a maqp of Africa and find out what you consider as 'West Africa'.
Liberia
Togo
Sinai Peninsula
Benin is not in Cameroon. Benin and Cameroon are two separate, independent countries.
Cape Verde
Beirut
Tunisia
Sierra Leone
Gulf of Guinea
Harmattan
The capital of Nigeria is Abuja. It originally was Lagos.
Including islands, Cape Verde is the westernmost country in Africa. On the mainland, Senegal is the westernmost nation.