As of r8701, startup and shutdown of Slicer with only Volumes module selected in the Application Settings -> Modules results in memory leaks:

Class "vtkKWIcon" has 4 instances still around.
Class "vtkSlicerTheme" has 1 instance still around.
Class "vtkKWOptionDataBase" has 2 instances still around.
Class "vtkKWUNIXRegistryHelper" has 1 instance still around.
Class "vtkSlicerGUILayout" has 1 instance still around.
Class "vtkSlicerApplication" has 1 instance still around.
Class "vtkKWCheckButton" has 1 instance still around.
Class "vtkSlicerCheckRadioButtonIcons" has 1 instance still around.
Class "vtkSlicerGUICollection" has 1 instance still around.
Class "vtkStringArray" has 2 instances still around.
Class "vtkSlicerFont" has 1 instance still around.
Class "vtkSlicerColor" has 1 instance still around.
Class "vtkCommand or subclass" has 2 instances still around.