How can I enumerate display objects under a pixel relative to the stage?
Clarification: I want to write a function which get (x,y)
The hitTestPoint() method will get you information if a DisplayObject is at the specified point (http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/display/DisplayObject.html#hitTestPoint())
To get a list of objects you would have to recursively investigate all children of the stage, I don't think there is a predefined function for that.
Alternatively: What are you trying to achieve? Maybe you can just use events and make them bubble?