Saitô is the tenth most common Japanese surname.
People named Saitō include:
Saito Dosan (daimyō)
Saito Hajime (Shinsengumi captain)
Saito Makoto (former Governor-General of Korea, former Prime Minister of Japan)
Saito Mokichi (poet)
Saito Musashibo Benkei (fighting monk of folklore)
Fictional characters named Saitô
Saito, of Ghost in the Shell: Stand Alone Complex
Saitô Hajime, of Rurouni Kenshin
Kaede Saitou, of Angelic Layer
Saito Kayano of The Devil Does Exist
Kaori Saito, of Jiraishin / Ice Blade
Saito Hikari (Hub Hikari), of Rockman.EXE / Mega Man NT Warrior
Spoiler for the Rockman.EXE Saito: Saito Hikari is the unknown name of the protagonist. He is known much better as the one and only Rockman.EXE, the Net Navi of Hikari Netto, the second Protagonist. Saito (only in the game and manga) is Netto's twin brother, who had died of a disease. His father, Yuuichiro Hikari, had been unwilling to accept his son's death, and transferred his entire consciousness to that of a Customized Network Navigator. The two, unlike any pair of NetOp and NetNavi, begin to share a mental link, and have special powers known only to them. Unfortunately, in the Anime Series, Saito does not exist, and is just known as Rockman.EXE, and Rockman.EXE alone.
Second Note: There is a slight pun towards their name. Being an anime series focusing around that of the internet, they were named Netto and Saito. Noticing this, they are pronounced almost exactly like that of Net and Site.