Aim Assist is one of two Sniper's traits.
It gives +50% accuracy to all weapons. This doesn't have much effect with sniper rifles with perfect accuracy (and there are lot) but it improves Lynx much because it has low accuracy for a sniper rifle. Aim Assist has the best effect on Ion Cannon and Laser Cutter, because they have the lowest accuracy of all weapons that sniper can use. It also improves many weapons in gun games, but snipers aren't recommended to fight in gun games due to their low health.