Disease resistant apple trees: http://www.cumminsnursery.com/disease.htm

I've planted Liberty, Macfree and two other varieties from Miller Nursery. Note that they are disease resistant, not immune to disease.

Harlason is an apple variety that was developed at the University of Minnesota (if I remember correctly) and was selected for surviving the cold weather. That would be my concern more than not needing pruning.
http://www.minnesotaharvest.net/apple_haralson.htm