The ability do draw a line that can intelligently place stamps, textures, or others around it. For example, I could draw a line and ask it to place X stamp at X intervals with a size, rotation, whatever, and maybe also give it an <x,y> distance from the drawn line. This way, I could for example place a long line of hedges perfectly paralleled by a long line of fences, or maybe perfectly line a road texture with those hedges and fences, instead of doing it all by hand.