A diluted lacquer thinner that is "plastic friendly", causing minimal damage to plastic models. Can be used for any of the following:

Remove paint from paint brushes and other painting tools
Dilute Liquid Surface Primer allowing it to be used in airbrushes
Thin out putty such as Tamiya Putty (Basic Type)
Dilute lacquer based paints
Clean paint, oil etc. from various surfaces, including putty and actual model