Zyl is correct to celebrate the work of Mitsuishi Kotono. I'd like to add that she's also amazing as the Great Trouble Kanzaki in Great Teacher Onizuka.
I'm not a big fan of Kugimiya Rie's school of one-note, bitchy tsundere characters, but Mitsuishi Kotono's enthusiastic tsundere-before-it-was-cool Kanzaki is a joy. Mitsuishi Kotono > Kugimiya Rie. (This is the part where I figure out if I remembered to set Irssi to auto-rejoin. Kugimiya Rie fanboy channel ops are a petulant lot.)