Because I don't believe they've been mentioned yet, two other "insta-death" attacks that I was told about when learning martial arts, and an honorable mention:

• Kicking the inside of the thigh will create a deadly blood clot in the femoral artery - The concept behind this is that a sharp blow to the femoral artery will cause a clot, which will eventually go to the brain or heart to kill someone. It sounds vaguely plausible because there are many stories of people suffering trauma to the femoral artery, such as in car accidents, who die before anyone (including themselves) even realizes they're injured. The key here is that those injuries generally involve opening the femoral artery to the outside. With such a large artery, blood can exit the body rapidly, even fairly painlessly. And since the blood is moving from the heart to the lower limbs, it's unlikely for a clot to "travel up to the heart" to stop it. The more common injury from blunt force trauma is thrombosis from either a blood-clot or dislodged plaque.
• A sharp blow to the chest (aka the heart punch) - Yes, this can stop the heart, but it requires a lot of force and it's pretty random with the most likely times for it to happen are in a car crash (steering column) or baseball (baseball). It has been seen on occasion in boxing and in hockey, but it's a rare and random thing. Incidentally, this is also sort of the theory behind the thing you see in movies of striking of the chest of a dying person. The precordial thump can disrupt a dangerous arrhythmia of the heart, but it's a low-percentage maneuver which requires trained timing.
• Boxing the ears - I don't think I've heard of anyone suggesting this as a kill method outside of the playground where it was one of those scary rumors that some kid had died from having their ears boxed and the pressure was too much or their skull. Boxing the ears can rupture the ear drums, creating disorientation and deafness, but I cannot find a single case of anyone being killed by it.

Because I don't believe they've been mentioned yet, two other "insta-death" attacks that I was told about when learning martial arts, and an honorable mention:

• Kicking the inside of the thigh will create a deadly blood clot in the femoral artery - The concept behind this is that a sharp blow to the femoral artery will cause a clot, which will eventually go to the brain or heart to kill someone. It sounds vaguely plausible because there are many stories of people suffering trauma to the femoral artery, such as in car accidents, who die before anyone (including themselves) even realizes they're injured. The key here is that those injuries generally involve opening the femoral artery to the outside. With such a large artery, blood can exit the body rapidly, even fairly painlessly. And since the blood is moving from the heart to the lower limbs, it's unlikely for a clot to "travel up to the heart" to stop it. The more common injury from blunt force trauma is thrombosis from either a blood-clot or dislodged plaque.
• A sharp blow to the chest (aka the heart punch) - Yes, this can stop the heart, but it requires a lot of force and it's pretty random with the most likely times for it to happen are in a car crash (steering column) or baseball (baseball). It has been seen on occasion in boxing and in hockey, but it's a rare and random thing. Incidentally, this is also sort of the theory behind the thing you see in movies of striking of the chest of a dying person. The precordial thump can disrupt a dangerous arrhythmia of the heart, but it's a low-percentage maneuver which requires trained timing.
• Boxing the ears - I don't think I've heard of anyone suggesting this as a kill method outside of the playground where it was one of those scary rumors that some kid had died from having their ears boxed and the pressure was too much for their skull. Boxing the ears can rupture the ear drums, creating disorientation and deafness, but I cannot find a single case of anyone being killed by it.