Trout
Actually, the stance isn't part of the swing at all. That's just personal style. The swing starts at front heel plant. That's why you see so many different stances in the MLB, but if you slow down the video, most hitters have extremely similar mechanics from front heel plant through extension. Crazy stances like Youkilis' require a lot more work to get the back elbow slotted, but if the hitter has the muscle memory to do it, it doesn't make hardly any difference in the swing.
I love watching great hitters swing...here's a assortment of current players. Talk about head on a swivle.
I realize who I'm arguing with here, but I have to disagree. Look at the Ted Williams video I posted above. He is clearly planting his heel. As he torques his hips, his foot turns on the axis of his heel.
Here are some more videos clearly showing a planted front heel.
Pujols: http://youtu.be/V89JddTPKB4
Trout: http://youtu.be/fzpAJkq-BDs
Harper: http://youtu.be/Dgwi-AODnn8
Griffey: http://youtu.be/W3NF23Cs1m4
It would be virtually impossible for Harper and Griffey to be able to make contact with their back foot completely off the ground or for Pujols and Trout to drag their back foot forward during the swing if they didn't have their heel planted.
Lastly, the bulldog in your avatar also has his heel planted.
Talk about head on a swivle.