Raycasting.
Oh, didn't read that aiming part, lol.
Edit:
To shoot a raycast, here is the code below:
//%player should be defined above
%eyeVector = %player.getEyeVector();
%eyePoint = %player.getEyePoint();
%range = 100;
%rangeScale = VectorScale(%eyeVector, %range);
%rangeEnd = VectorAdd(%eyePoint, %rangeScale);
%raycast = containerRayCast(%eyePoint,%rangeEnd,$TypeMasks::PlayerObjectType, %player);
%object = %raycast.getId();
if(isObject(%object) && %object.getClassname() $= "Player")
{
//Execute code if player is looking at someone.
%objectName = %object.client.name;
}