It's debatable whether Suzumiya Haruhi is a tsundere, but from my point of view, she's more a tsuntsun type character
Deredere is the opposite of tsuntsun. A deredere character is often uncertain and needs a push to get going. Nerine from Shuffle! and Mikuru from Suzumiya Haruhi can be considered as deredere characters.
Come to think of it, Sakura is also a deredere type character...
Now we have tsundere, the combination of both tsuntsun and deredere traits. A tsundere is a person who starts off with a tsuntsun type personality but ends up with a deredere personality. They are the serious, highly ambitious and confident type but slowly develops or shows signs of deredere, usually developing feelings for another character and dropping the tough front.
Tsundere's are usually female lead characters, but the term itself is not gender specific. Some of the more popular tsundere characters includes -
- Hiiragi Kagami (Lucky Star)
- Narusegawa Naru (Love Hina)
- Shana (Shakugan no Shana)
- Tohsaka Rin (Fate/Stay Night)
- Tendo Akane (Ranma 1/2)
- Social Web