Kyon

Kyon is the second person to join the SOS Brigade, and unintentionally gave Haruhi Suzumiya the idea to form the club. He is the "fourth seat" of the group. He is the only member of the group who is "normal", having no special abilities at all. He is enrolled in North High, and his real name is unknown, his nickname Kyon was created for him by his aunt and then spread by his little sister.

Source: Haruhi Wiki