My favorite to flick open was my Sage 1. But I flicked it about a hundred times one day while watching a movie and it started grinding a bit. Threw some oil in the pivot and it was fine.
Now I flick my PM2 all damn day and it's awesome. I love playing with my PM2.
My favorite to flick though is my GB1. During open and close it sounds like a rifle cocking, lol. But my GB is also my worst one to flick because it's difficult to do. Many times I've just scraped a layer off my fingernail and the blade didn't budge. You know, that sharp edge on the hole and everything, haha.