List of the characters that are taken by someone else will be in this topic. Remember, someone might play adult Sasuke and you play the kid version. As long as they don't look alike, it's fine. The avatar you choose only defines your appearance, your soul is not related to Sasuke from the anime Naruto. You only look like him. Your backstory, psychology, and abilities will be totally original and created by you. You can also choose to copy abilities from any show or anime, but make it slightly different and change the name.
The following characters are taken, therefore unavailable:
Obito Uchiha