I've started these three Light Side characters already so you're free to pick any of these on the Light Side:
Since I would start my last Light Side character as a "Smuggler".
I've only started one Dark Side character, the Imperial Agent, so if you go Dark side you can pick any of them and I'd just fill with one of the three classes I haven't started.
Note that there are also two "sub-classes" associated with each class. They don't change your character's story but their abilities will be different if you want to read up on them.
Last, all of my characters are on the "Satele Shan" server so make sure to join that server. You can switch server's later but it's a little bit of a pain.
Probably free this coming weekend (or all week really) so just let me know when you wanna play, @targetrasp