Thou shalt not steal. Exodus 20:15
To be honest I don't have much to say about this one that I didn't say about #6. It sounds good on the surface but is too vague to be truly useful. There are plenty of reasons that stealing might end up being ethical in certain situations. If it were to save someones life for instance I would be willing to steal, this law seems to fail to make any such exceptions.
The other thing about stealing is that the concept goes hand it hand with the concept of property ownership, just about every sufficiently developed society in human history has developed this concept, usually about the same time they traded hunter-gather culture for that of an agrarian one. The point is that the idea that, in general, we shouldn't take others stuff is not unique to Christianity and requires no god to mandate it. Stable societies require such a law if they wish to stay stable. It seems to me there is no real way to claim that our founding fathers only made theft illegal because the bible said so, even if they were super religious. Plenty of societies prior to Judaism's advent made this a crime and plenty since.