shana
Shana is the main heroine of the Shakugan no Shana media franchise.
She is the Flame Haze bound as contractor to the Crimson God Alastor; their job is to stop other Crimson Denizens from running amok. The series begins when she gets involved with Sakai Yuuji, an ordinary high schooler who's been imbued with a powerful artifact that can't fall into the wrong hands. Shana becomes his protector, and gradually more like a partner as he learns to fight; in turn, sharing daily life with Yuuji gradually brings Shana out of her shell (she's always lived in the world of Flame Haze, to the point of not even bothering with a name till Yuuji gives her one).
Shana is often seen wearing a pendant, the vessel of Alastor, and wielding the sword she's named after, the Nietono no Shana. She sports long hair (black normally, red with a flame effect when she's fighting), an ahoge, and zettai ryouiki. Her closest connections are with Alastor (partner and advisor), Yuuji (love interest), Yoshida Kazumi (friend/love rival), and Wilhelmina Carmel (mother figure). Her love for melon bread is the stuff of legend.
While not the first tsundere character, Shana is rivalled only by Tohsaka Rin for most famous one.