Walk into class JUST as the bell rings. Not one minute before or a second after, so technically you're not late, so the teacher can't give you a tardy. But you walk in at the EXACT moment the bell rings, which is sure to annoy any teacher.
Drop your textbook. This works especially well if you have a thick or large one. Don't make it look too obvious, like you're doing it on purpose. For instance, while you're writing, you could "accidentally" shift your wrist too fast and knock the textbook on the floor, creating a loud and satisfying THUMP.