This is pretty much all the characters voiced by Kana Hanazawa in one post. Though it's not much of a seiyuu joke.
Potemayo
PotemayoKajiwara Sora
Sketchbook ~full color's~Chiaki Kurihara
Miniskirt PiratesBlack★Rock Shooter (Mato Kuroi)
Black★Rock ShooterSonohara Anri
Durarara!!Kaminagi Ryouko
Zegapain"Tenshi"/"Angel"
Angel Beats!Charles/Charlotte Dunois
Infinite StratosSengoku Nadeko
BakemonogatariRoromiya Karuta
Inu X Boku SSKurashita Tsukimi
KuragehimeSusukihotaru
Otome Youkai ZakuroZessica Wong
Aquarion EVOLMatsumi Kuro
Saki: Achiga-henGokou Ruri/"Kuroneko"
Ore no Imouto ga Konna Ni Kawaii Wage ga Nai!Noir Vinocacao
Dog DaysHasegawa Kobato
Boku wa Tomodachi ga SukunaiHyuuga Mahiru
Kamisama DollsZange
KannagiMoriyama Shiemi
Ao no ExorcistShiina Mayuri
Steins;GateShiomiya Shiori
Kami Nomi zo Shiru SekaiYuuki Mikan
To Love-Ru seriesSuou Pavlichenko
Darker than BlackMinato Tomoka
Rou-Kyuu-Bu!Nessa
FractaleHanato Kobato
Kobato.Naruse Kozue
Seikimatsu Occult Gakuin