Here are some of my favorite 2D girls.

1. Nagato Yuki (長門有希)—Suzumiya Haruhi no Yuuutsu
   
2. Takino Tomo (滝野智)—Azumanga Daioh
3. Mint Blancmanche (ミント・ブラマンシュ)—Galaxy Angel
4. Kuurubiyuutei Gankyou (空琉美遊亭丸京)—Joshiraku