A free rehearsal mark font with serifs (created by Jari Williamsson), specially designed for the new Rehearsal Mark expression style that was introduced in Finale 2010. In the Expression Designer, put  the rehearsal mark style between any of the [], {}, (), {} brackets to get automatic enclosures. Like this:

After the new rehearsal mark style has been created, you probably want to assign a metatool key for it (so the process to add new rehearsal marks to the score gets really quick and easy). The Finale 2010 default files use M as the metatool key for rehearsal marks, so to get that same behaviour press Shift+M in the document (while the Expression Tool is selected) to program the metatool key to use the new Rehearsal Mark style.

If needed, edit the Score List for the Rehearsal Marks category as well to make sure the marks show correctly in both score and parts.

Samples: