While I was reading through the books it struck me that Gravitation would be the most useful surge for an archer to have by far, and would probably actually be quiet overpowered. Think about it. Using Gravitation a Surgebinder can change the direction in which objects fall. This means they could essentially aim a projectile in a direction and - as long as it had enough Stormlight - it wouldn't deviate from its path at all, essentially giving them perfect accuracy against stationary targets and unlimited range. Not only that, the arrows would increase in speed and power the further they flew. A Windrunner or Skybreaker in plate with a Grandbow could do a lot of damage from insanely far away, without needing any real bow skills, since they are basically dropping arrows on people.