That includes anything that we as believers might do, think, or say. Paul's reason for including this last element is to fill out the list. Angels and demons are created beings. They can't separate us from God. Neither can any other created being.
Every human being falls in the category of a created being.
Before turning off my Mac I feel compelled to respond to a very dangerous assurance teaching which is about today. There are many who would agree that one cannot lose his salvation and yet they say that no one can be sure he personally is saved. They suggest that no one can know for sure if he has been saved yet-at least not till death. That would be a ridiculous statement if I can't know that Christ loves me. As long as I doubt his love for me I will be robbed of the motivating power of gratitude.