I use the "other" technique when it's necessary for the user to be able to mix in their own:

    enum WidgetFlavor
    {
        Vanilla,
        Chocolate,
        Strawberry,
        Other=10000,
    };

Now users can add their own (and are also responsible for making sure it works in all APIs):

    enum CustomWidgetFlavor
    {
        RockyRoad=Other,
        GroovyGrape,
        Cola,
    };

And now you can amend the enum without breaking the client:

    enum WidgetFlavor
    {
        Vanilla,
        Chocolate,
        Strawberry,
        Mint,
        Other=10000,
    };