Formal:
* Non vedo l'ora di vederti. (This is the most common and literal translation, meaning "I can't wait to see you.")
* Aspetto con ansia di incontrarti. (This is slightly more formal and means "I anxiously await our meeting.")
Informal:
* Ti aspetto! (This is a very casual way to say "I'm waiting for you!")
* Non vedo l'ora di rivederti. (This means "I can't wait to see you again" and is more appropriate for someone you know well.)
Romantic:
* Non vedo l'ora di incontrarti di nuovo. (This means "I can't wait to see you again" and is more romantic than the other options.)
* Ti penso ogni giorno e non vedo l'ora di rivederti. (This means "I think about you every day and can't wait to see you again." It's quite romantic and passionate.)
The best choice will depend on the specific situation and your relationship with the person you are speaking to.