Once upon a time, I would have just assumed the answer to this question would be ‘yes’ for every living human being in the first world. It recently came to my attention that two people I know personally - one being my wife - have never done this. Furthermore, they both refuse to do so now that it’s been brought to their attention. So now I’m curious…
Yes I have. I didn’t like it. 
Yes. It’s how to check voltage without a voltmeter.
Female - yes, because I was told not to.
How else am I supposed to check a 9V battery?
Yea, all the time.
I have to keep them away from my niece. She’ll hold one to her tongue for hours at a time.
I’d never heard of doing such a thing until I was in college. (I imagine my parents would have treated putting batteries in your mouth along the same lines as sticking a fork in an outlet.) Used it all the time to make sure the batteries in the wireless mics were fresh.
Sure! Nobody told me not to.
I have. Perhaps in the age of iPods and iPhones, 9 volt batteries are less relevant.
Nope, never done it, and, as has been said, now that I’ve heard so much about it, I can’t get myself to do it. Same goes for getting a piece of foil in my mouth (against my fillings).
Oddly though, I’ve had plenty of 120v shocks and getting another isn’t exactly something I live in fear of. Assuming it doesn’t actually kill me, it’s not all that painful.
Yep, although it’s been many years. The strange thing is, that I can taste it and feel it now–a powerful memory.
A few days before we got married, my almost-husband and I were packing up stuff to take from my parents’ house. There was a stray 9-volt battery in the mess. I mentioned something along the lines of “I’ve heard that you can test a 9-volt with your tongue.”
Almost-husband said, “Nah, it’s not true. I’ve tried it, and there’s nothing to it. Here, you try.”
I did.
Of COURSE I got zapped!
I looked at him with horror, thinking, “I want to spend my LIFE with someone like that?”
We celebrated our 37th anniversary at the end of June.
~VOW
still used in smoke alarms and some radios for power or backup. still an approximate test.
My first reaction to the question was, “Who hasn’t?”, but clearly many of you haven’t. Wow.
For me, I’m pretty sure it was my dad who taught me I could check batteries that way. I had the best dad. I miss him.
I’m sure it’s been asked before, but how else would you know the thing is charged? 
Zapped? That’s a considerable exaggeration.
Many moons ago I had Tandy Championship Football (the top one) and I played it so much that I broke the Pass button three times (my dad fixed it each time). It ran on 9-volts and so I had little choice but to test the battery frequently lest I lose a game in the middle of a typical blowout. Out came the tongue, as it were, since I can’t stick mine out, and when I got a nice warming sensation to go with the metallic taste I knew was good to go. Even at age 6 I never thought it was a big deal, and it still isn’t.
It would never occur to me. Had no idea this was a “thing.”
No, but I stuck the end of a 12 volt adapter in my mouth once. I imagine the effect is pretty similar.
Why the hell…Never mind.
I’ve never even heard of doing this before.