Puppetry Technique: The favorite skill of Akasuna no Sasori, it turns opponents into puppets while retaining their abilities. However, this is a forbidden jutsu that people dare not use as it will make them public enemies. Sasori himself is a puppet, so he doesn't care about his cruelty.
Reaper Death Seal: Jutsu frequently used by Orochimaru, also used by the Fourth Hokage and the Third Hokage. It is powerful but comes at a high cost, so it is not commonly used. I think Kakashi, as a ninja who copied countless ninjutsu, might be able to use it, although it has not been shown yet.
God's Paper Technique: Jutsu that detonates 600 billion explosive tags to kill Tobi. This jutsu is extremely powerful but also a mutually assured destruction technique. Unless it is a desperate situation, people generally would not use it.
Dragon's Rebirth: Jutsu that resurrects others at the cost of your own life. Although it only appeared in the Naruto movies, for Uchiha Madara who desires true resurrection, it is a technique he is very eager to learn so that he can control others to resurrect himself.
Izanami: A powerful jutsu that is the nemesis of Izanagi. The fact that Yakushi Kabuto was perfectly redeemed is the best evidence. Uchiha Itachi used his eyes twice at the cost of becoming blind. However, killing other Sharingan wielders is also an option, but this would anger the public, so it should be avoided unless necessary.