3. Earth-1 Harrison Wells
Season two brilliantly found a way to bring the great Tom Cavanagh back into the fold by offering a completely different, yet recognisable, version of Harrison Wells – his Earth-2 equivalent who joined Team Flash until he returned to his Earth in the finale.
Now that Barry has changed time, this opens up the possibility for this same trick to be repeated and for another previously unseen version of Wells to turn up. In the finale, Barry incapacitated Eobard Thawne, so he will surely not be free to kill and take Harrison Wells’ form in this timeline. That means that the original Harrison will now be alive and well(s).
Presumably he will fill the Thomas Wayne role in the Flashpoint arc and help Barry return the timeline to its original form, even if it means that he will be dead. Expect Cavanagh to knock it out of the park yet again here.