Red Skeleton

A skeleton variant that spawns in strongholds and perhaps in mineshafts. As the name implies, it's a skeleton with a kind of pinkish red hue, almost like faded blood. It's stronger and more aggressive than normal skeletons. It wields a bone as a club, but it can also toss bones at players as a projectile. When it is defeated it does not die, it crumbles into a pile of bones on the floor that will revive after 5 or 6 seconds with half health. There are two ways of killing red skeletons: slay it with a sword that has the smite enchantment, or set it on fire when it is crumbled on the ground with flint and steel, lava, or a weapon that can set enemies on fire. Or when it's on the floor, the player can quickly wall in the red skeleton with blocks before it is reanimated. 

On death it drop bones, red dye, and a slim chance to drop its head. 

Red skeletons give players a reason to consider smite instead of sharpness when enchanting weapons, and being mostly in strongholds, give the penultimate dungeon more of a challenge before facing The End.