I've been teaching martial arts now for just short of 35 years, and have branched out quite a bit from my first few styles. So I know a thing or two about martial applications.
Folks who work with me a lot - particularly the men - can tell you I'm not shy about tapping target areas, so long as safety is maintained. For instance in the Seisan bunkai "groin strikes," I'm all about people going for the target. Particularly in the "official" bunkai where they have you going for the less-probable rear hit application, I think it's important for people actually to work on getting the hand RIGHT ON the target. From years of working with people in contact martial arts and having done surgery in the lab for 4 years, I can hit a target on someone blindfolded if they touch me or I them. Meanwhile, those who don't target are terrible at doing it, and I fear wouldn't be able to pull that technique off when they needed it. For my guys who I know wear cups, I demonstrate by swinging my hand half an inch from the package, and then knocking on the cup to show folks I'm right where I want to be without even seeing it.
One class of targets I try to teach people are what Bruce Miller likes to call reflex points. These typically can be found at joint folds, but are in other areas like the suprasternal notch. Most trigger the dynamic stretch reflex and cause the joint to buckle. In the case of the suprasternal notch, it triggers the gag reflex. The good thing about these targets is that they still work when someone is in the extreme range of neurohormonal stimulation, and they still work if the person is drugged (but standing and conscious). That isn't the case with target areas or grappling techniques that rely on pain to work.
One of my favorites, and one I learned from Okinawa sparring champion Mayamia, is the femoral crease. I never thought much of the Uechi sokuto geri until Mayamiya showed me how you can grab a person's arm and fold them in half by fitting the foot blade right in that crease. The angles are perfect, and it works like a charm. Mayamiya says that he uses it to "cut those tall Americans down to size."
(FWIW, he's a perfect gentleman. He just knows how to fight.) The target area is also suggested by the opening of Sanchin kata. While those thrusts can be used in many locations, a double shot to the two femoral creases will cause someone to buckle at the hips. If not the nukites, hirakens or seiken fists work just fine.
So there I was yesterday teaching the technique to Elizabeth, one of my new kid students. She's home schooled, so karate class is a chance for her to get out. While a lot of kids these days don't go for karate, this is a big thing for this precocious but sheltered kid. And we all love her.
Elizabeth is 12, and puberty is just kicking in. Normally everyone is just "a student" in class and I don't make a big deal when body parts are touched. It's all a very professional and clinical atmosphere, with some light-hearted joking when appropriate. But when it came to me showing her how double hand thrusts to the femoral creases could make the body buckle, I paused. That little voice in my head said that perhaps I should skip this lesson until another day.