Expensive, but Adidas Ultraboost Uncaged is the most extraordinarily comfortable show I've ever tried. The upper is like a sock, and the sole is a patented energy-returning foam that compresses and "bounces" back with every step. Super light, flexible, and impact is virtually non existent.
At $120-$180 a pair they are out of reach for many, but if you have a chance to try a pair on sometime, treat yourself.