Most people either love them or hate them; there is no inbetween.
Also the most infamously popular archetype in places around the world; not just OT. It's been suspected some so called fans like some tsundere girls just to the archetype alone. This hasn't quite been proven yet.
List of known ones (Some)
-Rin (girl in pic; Fate Stay/Night); Poster girl of a GOOD tsundere.
-Akane (Ramna) Prime example of a horrible type of Tsundere called the Takahashi Tsundere (named after her creator)
-Kagome- See above, but also has a tsundere boyfriend. Just one of many problems with Inuyasha.
-Kagami (Lucky Star); while it's more of minor tendencies it hasn't stopped people from forming a hivemind about her, making her the most popular character.
-Mio (K-ON); similar in nature to Kagami in addition to her looks seems to be following the trend.
-Louise (ZnT) Typical case of a JC Staff Tsundere (Take a loli-bodied tsundere, take out 90% of her deredere and replace it with twice as much Tsun); got such treatment the worse (She's not that bad in the novels)
-Haruhi; A rather hot genki girl who might be considered Kamidere as well, she's rather popular herself in this age of Season 2 delays and Yuki's popularity. Though I heard she's worse in the novels.