All bows have hand shock, and until someone makes a bow that is 100% efficient, they will continue to have it. As has already been pointed out by 7lakes, the excess energy stored in the limbs has to go somewhere at release. It is dissipated through limb vibration and riser vibration that is transmitted to the bow hand. That's what we feel as hand shock. Now some bows have less of it than others and some folks are less sensitive to it than others, but it's always there.
The major characteristics that lessen hand shock are bow design (high r/d bows usually have less), heavier, stiffer risers and lighter limbs as well as proper tiller, as Sixby pointed out, overall bow weight (heavier bows generally have reduced hand shock) heavier arrows, thinner, fast flite type strings, grip design, and of course the grip itself. The tighter the bow is gripped, the more the vibrating bow can work on the hand/wrist/arm. There are probably a few other causal factors as well, but that's most of them.