I think the last time I cried to manipulate someone, my age was in the early single digits.

Didn't work, either. But I wish I could say that I haven't been accused of it. I'm another person who cries out of anger or frustration. Not out-and-out sobbing, but it just comes out. The person I'm talking to is uncomfortable, I'm embarrassed, and I just ask for a few minutes to compose myself. Outside of family, this situation rarely happens at all.
There are a few sure-fire triggers that get me going. Being called something nasty, being slapped (hasn't happened in a long time, and won't happen again if I have anything to say about it, and I do), and getting yelled at are the three biggest ones. If someone is roaring in my face so that I can feel the sound waves inside my head, it has the same effect as a good slap would. I actively try
not to cry, and it makes it so much worse when I can't keep it in and the person keeps following me to continue the "conversation", aka make fun of my "weakness". One of the handfuls of times I've been in a blind rage was when someone insulted me to the point of tears and then mocked me by imitating the sounds I couldn't help making. It didn't get physical, but I honestly don't remember much after seeing red. He never mocked me again, though.
I don't cry to manipulate. I prefer to just be left alone until it passes, and I apologize afterwards for the awkwardness. People who employ actual crocodile tears to get their way in the supermarket or to swindle money out of relatives because they're "starving" or "won't make rent", then end up spending the money on, say, a new flatscreen TV (I've witnessed the former, but not the latter; that was a story I got from a co-worker who was complaining about a mooching relative) do
not have my respect.