If you can't save the days for another time, I would say that the most practical park for and hour would be MGM, as most of the board suggested. The closeness of those two great rides and the number of stores that are by there makes it easy to get a lot done in a short time period.
But I do agree that rather than trying to get as much in as you can, I would pick the one absolute favorite thing that you love to do in Disney and just do that one ride.
With Animal Kingdom being so big, I would avoid anything there because you will find yourself walking for most of your hour to and from the attraction that you want to see.
The wife and I usually reserve our last day to do DTD and get opur shopping and browsing done. It is a good way to wind down.
Good luck, have fun, and be safe.