private void AddDoubleClickEventStyle(ListBox listBox, MouseButtonEventHandler mouseButtonEventHandler)
{
    if (listBox.ItemContainerStyle == null)
        listBox.ItemContainerStyle = new Style(typeof(ListBoxItem));
    listBox.ItemContainerStyle.Setters.Add(new EventSetter()
    {
        Event = MouseDoubleClickEvent,
        Handler = mouseButtonEventHandler
    });
}

//Usage:
AddDoubleClickEventStyle(listView1, new MouseButtonEventHandler(listView1_MouseDoubleClick));

EventManager.RegisterClassHandler(typeof(ListBoxItem),
    ListBoxItem.MouseLeftButtonDownEvent,
    new RoutedEventHandler(this.MouseLeftButtonDownClassHandler));

private void OnMouseLeftButtonDown(object sender, RoutedEventArgs e)
{
}

<ListBox Name="testListBox">
    <ListBox.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}">
            <EventSetter Event="PreviewMouseLeftButtonDown" Handler="ListBox_MouseLeftButtonDown" />
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

myListBox.AddHandler(UIElement.MouseDownEvent,
        new MouseButtonEventHandler(ListBox_MouseDown), true);

<ListBox PreviewMouseDown="PlaceholdersListBox_OnPreviewMouseDown"/>

private void PlaceholdersListBox_OnPreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    var item = ItemsControl.ContainerFromElement(sender as ListBox, e.OriginalSource as DependencyObject) as ListBoxItem;
    if (item != null)
    {
        // ListBox item clicked - do some cool things here
    }
}