'Gag Factor 5' is a work of art. Especially Aurora Snow's scene. You'll never be the same after you see it. Also, 'American Bukkake 11' with Kiki D'aire and the "cumbong" is one to write home about.
Girlvert #2 is my favorite movie of theirs as well. I've enjoyed isolated scenes in some of their other series, like Gutter Mouths and White Trash Whore, but Girlvert #2 is, by far, my favorite movie of theirs.
American Bukkake is probably the nastiest porn series out right now, though it's not for everyone. The latest volume is number 19, and hopefully 20 will be out soon.
My fav. has definitely to be the Gag Factor series. Something about the mess that is made with all the spit turns me on immensely, although slapping can be left out.
I personally think the GGG series are better than the American Bukkake series.
You have to love the name of the official JM Productions website: jerkoffzone.com