Aho Girl

This 4-koma style manga features Yoshiko, a genuinely stupid girl (she can even manage to get all 0's on multiple choice tests). She hangs out at school with her childhood friend, who she claims to like, and he has to put up with all her ridiculous behavior!

(Source: MangaHelpers)

Included one-shot:
Volume 12: Nandemo Shiteageru (I'd do anything for you.)