UnityObjExporter

gameObject hierarchy to .obj/.mtl

An Editor script that parses through a gameObject and all its children, creating an .obj and .mtl file. Right now it only supports MeshFilters, and material support is limited to diffuse color (_Color) and texture (_MainTex).

Running

Add the script to an Editor folder. This will create the menu option File/Export Selected/.obj
As this suggests, the script starts from the selected gameObject, and traverses through all its children. Let it run -- I've found it to be decently fast even when creating .obj's with 500k verts (70MB) The .obj/.mtl and all textures are exported to Assets/objExport/gameObjectName.
This can be changed by modifying the line:

string dir = Path.Combine(Application.dataPath, "objExport/" + gO.name);

Support for additional shader properties can be added by modifying the function BuildMtl:

if (m.HasProperty("_Color"))
{
    Color c = m.GetColor("_Color");
    mtl.AppendFormat("Kd {0} {1} {2}", c.r, c.g, c.b).AppendLine();
}