Center torso is still often your best shot I think: - Head shots are typically too difficult and just wind up being wasted damage, barring powered down mechs or perhaps when shooting at an Awesome or Catapult. - Leg shots are great with certain weapons, especially if you're fighting one on one or coordinate with teammates to also aim at the legs, but in most pugs your teammates will aim CT regardless so you may as well focus fire with them. - Leg shots can be great for racking up your kill count once a match is won though, as whatever damage you do won't help those shooting CT, and you can always switch to CT at the last moment. ;-) That, and they're really easy to stick on mechs running away, where they'll often block torso shots with their arms. - I almost always shoot Atlases CT; you won't take it out all at once, but that's the only practical way to kill one, and once they lose their CT armor their firepower is dampened as they twist away to protect it. Not sure why, but I never leg them... probably because I typically only take them on with teammates.