For the apprentice my money is on Austin the Warlock from Zoo Day. He's already displayed 3 different magical abilities, all significant wizard level stuff.
1. Summoning multiple dangerous entities from the nevernever with zero prep work or ritual items.
2. Directed mental influencen strong enough to affect a wizard. Harry does blow it off pretty easily, but considering we've seen him power through very strong mental attacks with nothing but willpower, the fact that he used an actual spell to deflect austin's whammy is significant.
3. Ambient energy strong enough to affect entire crowds of people in the zoo, what harry describes as a place full of life and energy. Victor Sells was a full on sorcerer, and even he needed months of steady work to get his own house all dark and moody.
I know that Rat was pushing Austin, but the kid obviously has significant juice, several talents, and is leaning towards warlock already. Harry won't foist him off on the council, but austin clearly needs instruction or he'll keep hurting people.