Since we have all been in a situation which required writing a proper email, we all know that sometimes it can be difficult to think of an appropriate sign off. I've come across a link that has been very useful to me, so I decided to post it here. Maybe you'll find it helpful, too.
http://www.forbes.com/sites/susanadams/2013/09/27/57-ways-to-sign-off-on-an-email/