Szayel (Bleach) implanting himself in Nemu, and reincarnating himself into an undamaged form.
Eriol Hiiragizawa (Cardcaptor Sakura) is the reincarnation of Clow Reed.
Piccolo Jr. (Dragon Ball) is the reincarnation of King Piccolo.
Uub (Dragon Ball Z) is the human reincarnation of Kid Buu.
Greed (Fullmetal Alchemist) meets Ling Yao...
...and is reincarnated onto him.
Yuca (Immortal Rain) is the Spirit of Methuselah, and has constantly been reincarnating since the beginning of human history.
Kagome Higurashi (Inuyasha) alongside her past life, the priestess Kikyo.
Over the countless generations, Asura's and Indra's Chakra (Naruto) after their deaths have been reincarnated by different vessel's worthy of their chakra, one time Madara Uchiha integrated Hashirama's Cells and obliviously Asura's Chakra which he awakened the Rinnegan, their current vessels are Naruto who has Asura and Sasuke who has Indra.
Orochimaru (Naruto) using his "Living Corpse Reincarnation" to reincarnate himself into a new body, thus erasing any permanent damage and aging.
Two years after becoming a God Hand, Griffith (Berserk) was reincarnated on earth, with the full power of his God Hand form of Femto at his beck and call.
Mavis and Zeref (Fairy Tail) meeting once again after being reincarnated as Arius and Mio.