Post a character whose real name was not reveal/given until the very end o never reveal/given at all

C.C. her name was never directly told to the viewers

Heroine from Amnesia. Her real name wasn't revealed at the end of the series :D

Haku from Spirited Away
his real name was told in the end

Fourth Kazekage (Naruto Shippuden)

his name is not revealed in anime naruto shippuden......he was known as Fourth Kazekage.....but he was cool just like Gaara........gaara can control sand...but his father 4th Kazekage could control oro dust...its pretty epic.....he he eh eh

Kyon from The Melancholy of Haruhi Suzumiya, T.K from ángel Beats, and Taniguchi and Kunikida from TMOHS. Their last names were dado but not their first

From the daily lives of Highschool boys

The president(middle) and the vice president(left) of the student council XD even at the end credits they would refer to them as only president and vice president X3

Celestia Ludenberg from Danganronpa: The Animation, although her name wasn't reveal at the VERY end, but in the end of Chapter 3 of the game(around the end of Episode 7 in the anime version) her real name was revealed to be Taeko Yasuhiro

TK from ángel Beats never has his real name revealed por the end of the series.

All the characters of SAO