Totally depends on who I'm communicating with. I've never liked "regards" or any variant and have never used it. If I'm in a festive mood, it's usually "cheers". If it's a hawt chyk and I'm flirting, I might throw a "ciao" at her. If it's purely business I'll generally give the old bland "Thanks" or nothing at all.
In all seriousness, if we're talking about a business email then it's just a modern day memo that doesn't require a salutation. The standard at my office is that the last sentence is your sign-off, followed by your name (and in some situations, contact info other than email when appropriate).
If your email contains a response to requested info, you end with:
Please contact me if you have any questions or need additional assistance/information. / Let me know if this doesn't work for you./ I hope this helps. (depending on the level of formality)
If you're seeking something from someone else, then the following would be acceptable:
I look forward to hearing from you soon./ Thank you for your assistance./Your prompt attention is appreciated./ Thanks for your help.
If your email is a reply that rebuts or disputes the addressee's email, or if you are in opposing positions, then a respectful salutation is appropriate, such as:
If not covered in the body of the email, the last line covers your courtesy requirements.
If we're talking about emails between friends/family then it is whatever you like.