Light Yagami.

Because he is, in fact, quite dumb.

Log Horizon’s Shiroe, at least in Season 1 I haven’t seen anything newer. Its not that he is an absolute genius, but his plan to get all of the guilds working together while trapped in the world was really believable, clever, and it made complete sense as soon as it was revealed

Hammer

Probably Dexter or Jimmy Neutron.