Sample test addon to show using unregister() to remove changes by the addon

test_addon.py

bl_info = {"version": (1, 0), "blender": (2, 75, 0), "author": "myname",
    "name": "testing addon", "location": "blender", "description": "test a new addon" ,
    "warning": "only for testing", "category": "test", }
import bpy

# add your operators, panels .....

def register() :
    bpy.types.scene.my_int_storage = bpy.props.IntProperty()
    bpy.utils.register_class(myOperator)
    bpy.types.VIEW3D_MT_object.append(add_my_menu_item)

def unregister() :
    # remove all changes made in register()
    bpy.types.VIEW3D_MT_object.remove(add_my_menu_item)
    bpy.utils.unregister_class(myOperator)
    del bpy.types.scene.my_int_storage

if __name__ == "__main__":
    try:
        # by running unregister here we can run this script
        # in blenders text editor
        # the first time we run this script inside blender
        # we get an error that removing the changes fails
        unregister()
    except:
        pass
    register()