Nekomimi Shana and her huge ahoge on her head
Ahoge (アホ毛), aka silly hair or foolish hair, is a lock of hair that sticks out on an anime character's head.
It is a visual cue to identify/symbolise silliness, clumsiness, carefreeness or other similar character traits. A lot of characters (usually girls) have them across a lot of series, so I will just list a few examples here:
Saber from Fate/Stay Night
Konata Izumi from Lucky Star
Shana from Shakugan no Shana
(Different hair style and attire but it's still Shana there)
Other characters that have ahoge in the series include
Nakajima Subaru (right),
And Reinforce II from Mahou Shoujo Lyrical Nanoha StrikerS, showing different shapes of ahoge
Other characters such as Vita and Caro have them too.
Furukawa Naigsa from CLANNAD
Nagisa's ahoge is usually known as "hair antennae", as she has more than one lock of hair and are like those antennae of an ant. Her parents have them as well (i.e. hereditary ^^;)
Yukine (right) has an ahoge too - nearly forgot about hers too.
Minami Chiaki from Minami-ke
Chiaki's is rather special as it is shaped rather differently, and moreso it can move as if it's alive... o_O
Ahoge are not limited to girls only; guys can have them too (
Edward Elric from Fullmetal Alchemist, the ahoge can be seen on him and his chbi version on the club ^^;
There are too many characters with ahoge, and I may have even missed some from the anime series I have mentioned above (do tell me if I do). Do you like characters with ahoge, or is it something that hasn't bothered you much?
I feel that while ahoges can sometimes be insignificant as a physical cue to character apperance, they sometimes do add some characteristics and become part of the character. Imagine seeing Nagisa without her hair antennae for example, one may think that something missing around her (if you know what I mean).
Oh and an omake to finish off:
Konata door hanger, from げんれい工房
All anime screencaps are from Random Curiosity