Teaching Greek

I have taught Greek on a Seminary level for five years now, having used
four different textbooks:  Machen, LaSor, Goetchius, and Hewett.  I have
reviewed numerous other grammars, but have still not settled on one as
"the" grammar.  I would be interested in what others of you who teach
Greek think of various grammars.
I would be interested for either seminary or college/university classes 
in Koine Greek.  
Gary D. Collier
University of Denver/Iliff School of Theology