Renderable Spline Modifier
Renderable Spline is a very useful and versatile modifier, that can prove useful in a variety of situations, like architectural modeling, 3D hair and many more.
Renderable Spline gives any splines you have drawn out a 3D presence in the scene, allowing them to be visible at render time. However, the modifiers use runs much deeper than that.
By setting the various properties in the attribute rollout you can get your spline shape exactly how you like. This will now show up in renderings. You could collapse the stack in order to edit the new shape by manipulating the spline elements. The next step is to convert this spline shape into a mesh or poly object, so you can work on it exactly how you would any other mesh object.
The above example was a line spline, Renderable Spline modifier applied, collapsed and then converted to a mesh object. Very useful for creating rooms for 3D architecture projects.