Deleting the "Accounts.db" file will allow you to bypass the message when you try to remove an android account from your phone (where it normally alerts you that you have to have at least 1 account present on the phone).
Rooted folks have a little more freedom :)
- Download Root Browser here.
- Delete the accounts.db file as shown in the video (If you're too lazy to watch the video, the file is located under /data/system/accounts.db).
- Reboot your device