This is a raw list someone compiled on Quora
- Darth Maul { Episiode I }
an unknown Nikto,
Vergere
Darth Tyranus/Count Dooku
Garth Ezzar,
- Darth Vader/Anakin Skywalker { Episode III - VI }
- Ferus Olin (informal apprentice) { The Last of the Jedi: Secret Weapon }
- Lumiya { Jedi vs. Sith: The Essential Guide to the Force }
- Luke Skywalker when Palpatine was in clone body { Dark Empire 5: Emperor Reborn }
He also had a bunch of people he trained who were not strictly speaking "Apprentices", such as Hands (e.g. Mara Jade); Prophet Cronal etc...