Red Skeleton

Blood Skeleton walks forward steadily, and instead of dying, just collapses into a pile of bones. It will soon reassemble itself, and can only be completely killed by a special weapon or spell.

Castlevania:Symphony of the Night
There are four varieties of this enemy: red, yellow, green and white. They act in the same way, except their speed and regeneration rate is different. Red are the slowest and white are the fastest.

Castlevania: Portrait of Ruin
These skeletons give a good amount of experience, but one needs to use the Undead Killer whip to kill them. They appear in Forgotten City and Sandy Grave.

Castlevania: Order of Ecclesia
These skeletons are called Blood skeletons in this game. They appear in Dracula's castle. Amusingly, Blood Skeletons can be vaporized by the Dominus Glyph Union, although that also kills Shanoa.