I'm going to have to agree with some of the other posters here. BM seems to do smooth actions pretty consistently for a production company. As a fairly poor college student, I can't afford some of the high end knives mentioned here but I can occasionally snag BM's which work out perfectly for me.
My personal favorite in my collection right now is my 746 Mini-Onslaught, thing is ridiculously smooth for a production folder and I think it may smooth out a bit more with a little use and another cleaning. My 940 is next up, then my 520, which feels slightly gritty. My 580 cannot really be felt since it is assisted.
Finally, like some others have said, the BM Dejavoo series are ridiculous. I can't believe how smooth those knives are. Wish BM would bring them back, along with a couple other models.