I did Ultimate Transpo w/ a Shapeshifter Color Change to make the switching visual, and the guy slowly opened his hand, stared at the card for about 15 seconds, goes, "What the ****?", and walks away. Everyone else was using curse words, as well. It was pretty neat. I don't think that's the best reaction I've ever received, but it was the best one I've had recently.
There is another kid that's a Junior (I'm a Freshman), but he's in my 2nd and 3rd hour classes. Well, one time I made the mistake of performing Morgan Strebler's "The Closer" to him, and now everytime I see him, he goes, "Drew! Bend my quarter!" He told one of his teachers about it, and I guess he was just holding the quarter the whole hour going, "How did he do that?" So that teacher came into my 7th hour class about 10 minutes after class started, and had me perform The Closer (that's obviously not what she called it), for the whole class... and now almost everyone in the school knows me for magic... and more specifically... for bending quarters.