A new MM font by Dirk Wachowiak (via ACME) called "Generation" features what might be called a Rigidity axis (although the font is sold only by the instance). One reported advantage of this axis is that it can be used to accomodate varying resolution, like screen versus print. Another is that it might allow for graduated variation in gender (feminine/masculine).
It seems to be viewable only at the German FontShop site:
Go to http://www.fontshop.de -> SCHRIFTEN, do a "SUCHEN" on "Generation", then click on it.
(Thanks to Jay Rutherford's mention in his ATypI "Country Delegates" report.)
hhp