To expand on Shinobu's answer:
These three (Shana, Taiga, and Louise, in that order) are commonly referred to as the "big three" tsundere characters. They each take a different perspective on what "tsundere" implies, but are the "guideline" characters when creating a tsundere.
These characters were all voiced by Rie Kugimiya, who has probably voiced the most tsundere characters of any voice actor.
Sometimes, due to fan's personal opinion, the "big three" is stated with other characters, often from Rie's portfolio. Common replacements are Nagi (Hayate the Combat Butler), and Aria (Aria the Scarlet Ammo).
However, it is generally accepted that the three listed earlier are the "big three", irreplaceable even with the passage of time. (Since fans have decided that "tsundere" is defined by the three's combined personality, and not the other way around.)
To dive into the strange side of anime for a moment; the "fans" I have been referring to are mostly those gathered around the TsunDere GiRlS RuLeS facebook page, and the corresponding wiki, http://tsunderegirlsrules.wikia.com.
(As a side note, Shakugan no Shana is well worth watching. (My favorite anime.))