Corey Anderson?
231 runs at 39 @ 110 SR
14 wickets at 16 @ 15 SR
Only weak point is his bowling economy.
As I said in the match thread, he'd have been favourite for shipping it if he was there till the end today. His numbers are very good, just needs a defining performance for him to win it. I think there is no one absolute standout performance (Sachin '03, Klusener '99) so the MOTS has a heavy chance of being from the winning team.
The 'If NZ win' MOTS selection is split pretty tensely between Guptill, who
will win it if he tons up as he is also a few runs away from being top scorer of the WC, McCullum who has set the tone for this NZ side and has had massive balls both as a captain and a player, Boult who will most likely end up as highest wickettaker of the WC and CoreyJ who is definitely the allrounder of the WC, one of them putting in a MOTM performance in the final leading to an NZ win will win it.
If Australia wins, Starc will most likely win it even if he is merely very good as opposed to invincible in these two games unless someone like McCullum puts in an ATG performance of his life in a losing cause.
Anyone from India is a far longer shot and would require one of Kohli/Dhawan/Shami to put in a top two players in the ODI performance in two consecutive games.
Starc at this point is the single most likely contender IMO as Australia have about as much chance as NZ to win it and Aus top performer is far more obvious at this point.
Two games, specifically when they are the semi and the final can change a lot of things though.