Action won't go away! This is very annoying. I need to delete an action I keep hitting x and clear animation data and all that, won't leave! I have quit and reopened, there is no 0 next to the name.
To unlink datablocks from the blend file hold Shift button and click on the X icon of the datablock. That will set the number of users to zero and it will not be saved in the blend file.

Remember to reload file after saving it.