Pebble
Because Zuko likes to talk trash, and Toph sure as hell isn't gonna take it lying down!
Zuko groaned as an impossibly tiny knee dug itself into the small of his back. He was vaguely aware, somewhere between the ache in his chest and the burning in his right arm, of the hand fisted in the collar of his tunic. If he turned his head just the tiniest bit, he knew he would see the waterbender, with one of those trying-not-to-choke smiles on her face. He could hear her idiot brother laughing like a maniac.
The ground did not taste too good.
"What did you call me, Princess?" an angry voice demanded. If Zuko's brain had been functioning properly, he would have remembered the insult he had given that had landed him laid out flat in front of his uncle, two peasants, and the Avatar (who was snickering behind his hand). The voice seemed to know he couldn't come up with an answer, and the hand attached to it proceeded to rub his face into the dirt.
The knee lifted, and the earth shifted under him, rolling him over to face the sky. A head appeared: that young blind girl, the one who would be helpless against a firebender…
Oh. Right.
"The next time you wanna call me helpless," Toph spat angrily, "remember what dirt tastes like!"
Then she dropped a pebble on his forehead and stalked off.
AN: Ah, sweet beginnings. This will be a place for me to post any and all drabbles involving interaction between Zuko and Toph. Because, let's face it, watching them is gonna be hilarious. Some will be Zuko/Toph (Zoph? Tuko?), some won't. This one wasn't.