Illustrator :: Separating Object Into Multiple Objects With Pen?

I'm looking for a way to draw a single, solid object and then divide that object into multiple objects using the pen tool; not other objects.
 
Ex: Draw a solid cirlce, use the pen tool to draw lines over said circle (visually creating different shapes), then [do something] with both the original circle and the pen-drawn lines to actually create the new shapes/objects. 
 
I've done this before by placing other OBJECTS over the original object and then using the divide or trim pathfinder toggles, but using other shapes (even the line tool) has its limitations.