Suzumiya Haruhi no Yuuutsu ED
(Melancholy of Haruhi Suzumiya)
“Hare Hare Yukai (ハレ晴レユカイ; Sunny Sunny Happy)” by Aya Hirano, Minori Chihara, and Yuko Goto
used as ED for episodes 1 – 13.
One of the most influential ending to be ever produced, because of its infamous choreographed dance. At the time when it’s airing, there were even a lot of fans trying to imitate the “Haruhi Dance”. Even anime tries to copy this ending. Future productions by Kyoto Animation, like “Lucky Star”, as well as those by other studios, such as “Carnival Phantasm”, try to take a page out of Haruhi to this day.
Lastly, did I mention how much I love it when voice actors for the protagonists double as leads for OP and ED songs?