#3 Sasha Banks

This may not seem all that likely, but Sasha Banks winning the Royal Rumble match makes a lot of sense. For one, her match with Bayley is perhaps the only match on the WrestleMania 36 card that seems like a certainty. No other challenger for the SmackDown Women's Championship comes close to the Legit Boss.
It would also be a wildly unpredictable victory, as Sasha has been playing second fiddle to Bayley for a while now. She is good enough to pull it off. The 4-time RAW Women's Champion was the iron woman in the first-ever women's Rumble match and could do the same once again.
It is a crying shame that the Boss is yet to receive a lengthy title reign on the main roster. That misstep has to be corrected at WrestleMania. But a shock victory at Royal Rumble could ramp up the excitement for the impending program with her best friend.
WWE could tell a similar story with Bayley and Sasha Banks, to the one they did with Triple H and Batista. A win for Sasha is unlikely, but it has the potential to be something special.