1. Shark Skin: Combining the Jinchuriki and Samehada abilities, the "Shark Skin" fusion allows the Jinchuriki to continuously absorb chakra, similar to tailed beasts. However, if chakra is insufficient, Samehada may harm its owner.

2. Inuzuka Clan: The Inuzuka clan can transform into two- or three-headed wolves, increasing their power, by using their fusion technique. However, it has limited effectiveness against strong enemies.

3. Susano'o: The "Susano'o: Wrathful" fusion combines the power of Susano'o and the Nine-Tails. Used in the Fourth Ninja War by Madara Uchiha, Naruto, and Sasuke, this form is stronger than the separate tailed beast and Susano'o.

4. Ghost Merge Jutsu: In the movie "The Will of Fire," Hiruko uses the forbidden "Ghost Merge Jutsu" to merge and absorb other ninjas' powers. While granting immense strength, the combination of ninja and animal spirits may seem odd.

5. Art of Twin Demons: Righto's unique bloodline limit, the "Art of Twin Demons," allows him to infiltrate an enemy's body and gradually corrode their cells, causing death. Kabuto Yakushi also used it controversially, resulting in a disturbing fusion with various individuals. (97 words)