I can do that, but a. it's real emotion involved and b. it therefore takes a good long while to get myself into that state; not to mention c. I can't always do it. Which leads to d. this would be utterly useless as a tactic to manipulate someone else, as I usually see fake tears described.

I'm sure plenty of people can do it, but I don't think I have a single friend or family member who is capable of and/or has used this tactic.

I should -- I do, actually -- count myself blessed for that.