My first recollection of a wonderful open mouth inhale came in my childhood days from a movie called Long Gone starring Virginia Madsen. If you have never seen it, you should look it up. Some wonderful smoking from a young Madsen.
Now check out this beauty. Two pictures as she offers a nice little open mouth inhale.
Next up are a couple of beautiful blonde smokers as they perform wonderful snap inhales.
It is so wonderful seeing that exact moment as the girls pull the smoke deep into their lungs. The concentration on their faces and in their eyes says it all.
Finally I'll leave you with these two young smokers to round out the set of open mouth inhales as they show off a bit of smoke before inhaling deeply and letting loose a long exhale.