I've also been thinking about one of Mowzie's older ideas of a possessed suit of armor that tries to out itself on the player and I've been coming up with ideas that expand upon it XD
What if for the possessed armor, it's actually being controlled by a floating heart with an eye at the center of it that's hiding inside of it. Standing about half a block higher than the player, it could be an elite enemy that wields a longsword and shield, and it's attacks could include basic melee attacks and blocking, as well as throwing pieces of it's armor at the player. However, the player would be able to knock these pieces of armor to the ground by hitting them at the right time, causing the heart to lose a piece of it's armor.
If the player manages to wack away enough armor pieces, the floating heart will be exposed, allowing the player to go in for the killing blow. If the player fails to attack the heart quick enough, the heart will start collecting it's lost armor pieces again. This was just a quick little brainstorm I decided to post XD