Hiashi Hyuuga, Hanabi Hyuuga... Almost every Hyuuga except Neji and Kou (a branch house member whose name is only mentioned once).
With Hinata, it actually goes a step further. Both her given name and family name can be written with the exact same kanji, although only her family name is officially written in them, with her given name written in katakana.
Had Naruto taken on his father's last name, he would be Naruto Namikaze.
Alice Alice Arquet and Maggie Mui from ROD the TV.
Bleach: Kubo chooses names and language themes based on how words sound to him so this crops up a few times. Examples include Ouetsu Nimaiya's Sword Five girls, Aaroniero Arruerie, Bambietta Basterbine, Candice Catnipp, NaNaNa Najahkoop, and Giselle Gewelle (both names start with a soft-g to produce a "jheh" sound despite the "gi" and "gi" spelling). Averted with Loyd Lloyd, as the spelling variation changes both the letter and sound.
B Gata H Kei represents with Mayu Miyano, Kazuki Kosuda, Mami Misato, Kyouka Kanejou, and Keiichi Kanejou. One can only imagine that series protagonist Yamada, while suffering from a case of "No First Name Given", would follow this theme as well.
In the dub of Digimon Adventure, Izzy Izumi. Also Kari Kamiya and T.K. Takaishi. And T.K.'s given name in the original Japanese is Takeru.
Shiro Sanada in Space Battleship Yamato. Called Sandor in StarBlazers, in expanded universe material, he was eventually given the first name Stephen making both names alliterative. In the same expanded universe, Captain Avatar (originally Juzo Okita) was also bestowed with an alliterative name, as his first name (never mentioned onscreen) was made Abraham.
Solty Rei gives us the two main adult characters, Roy Revant and Miranda Maverick.
High School DXD gives us Asia Argento, The Medic of the group. Bonus points for her because her seiyuu, Azumi Asakura, also has the same initials.