This should be all of them, really the best / only source of documentation is the actual source code. This was found in /Library/UI/Skins/NavObjectBase.vb

Public Property CSSControl() As String       
Public Property CSSContainerRoot() As String
Public Property CSSNode() As String
Public Property CSSIcon() As String
Public Property CSSContainerSub() As String
Public Property CSSNodeHover() As String
Public Property CSSBreak() As String
Public Property CSSIndicateChildSub() As String
Public Property CSSIndicateChildRoot() As String
Public Property CSSBreadCrumbRoot() As String
Public Property CSSBreadCrumbSub() As String
Public Property CSSNodeRoot() As String
Public Property CSSNodeSelectedRoot() As String
Public Property CSSNodeSelectedSub() As String
Public Property CSSNodeHoverRoot() As String
Public Property CSSNodeHoverSub() As String
Public Property CSSSeparator() As String
Public Property CSSLeftSeparator() As String
Public Property CSSRightSeparator() As String
Public Property CSSLeftSeparatorSelection() As String
Public Property CSSRightSeparatorSelection() As String
Public Property CSSLeftSeparatorBreadCrumb() As String
Public Property CSSRightSeparatorBreadCrumb() As String
 

Unfortunately does the defenition of those values not mean that it works in the menu.

The following test have not passed my tests since the introduction of the DnnMenuNavigationProvider and the Nav skinobject.

Corresponding css file

 .CssSeparator
{
    border-style: dashed;
    background-color: #FFFF00;
    color: #00FFFF;
}