Between Panarin, Marchand and Stone for me. Panarin because of his offensive contribution without being a huge defensive liability like Kane, and Stone and Marchand for their offensive contribution while being possession beasts and great and good (respectively) defensively.
Kucherov is a bit of a wild card, we know what he's capable of but it will be interesting to see what impact his injury has had.
Rantanen and Marner are making a case for themselves if they can continue playing like they are in the upcoming seasons.
Kane isn't in the convo for me anymore. He's still great at creating offense, as he has always been, but he's a disaster on the other end, unlike the other aforementioned players, and his offensive contribution doesn't justify putting him above the others. Playoffs pedigree, I guess, but his insane runs were more than half a decade ago.