List of all objects considered as GUIElement

Hi, I'm trying to use Unity's built in

OnMouseDrag()

It says it drags only GUIElements or colliders. What are considered GUIElements? GUI.window? GUI button/repeat buttons?

Thanks a lot!

GUIText and GUITexture

Basically, the things which inherit from GUIElement, here:

http://unity3d.com/support/documentation/ScriptReference/20_class_hierarchy.html