Classes tagged with the Blueprintable specifier can be inherited by Blueprints and, as such, this specifier sees frequent use throughout the Engine and in game-specific implementations. For example, tagging the following class with this specifier enables one to create a Blueprint from it in the Editor:
UCLASS(Blueprintable)
class UCoolComponent : public UActorComponentThis specifier can be applied to all derivatives of the UObject class, including Components, Actors, and direct descendants of UObject.