createNode implicitSphere -n "name";
createNode implicitBox -n "name";
createNode implicitCone -n "name";
Each of these commands basically creates a non-renderable object (sphere, cube, cone) that has a very basic shape node (no components) and a transform node. You can still go into the shape node and change color using the drawing overrides and all. Doubt I'll be using them all the time or anything, but cool to know they are there if ever you should need them.