Poll forthcoming
Chopping the final letter off my middle name makes a suitable surname for signing silly letters like this one, but otherwise I only go by my first name. Even when I worked with preschoolers, I was “Miss Shannon” rather than “Miss [surname].”
I was under the impression that people who go by their last name are mostly law enforcement, military, or sports players.
Or MacGyver.
The short form of my first name.
I go by my middle name, but am sometimes known by my last name to people, and don’t work in anything related to any of those fields. My experience is that being called by your last name is not at all uncommon for men.
“De”? 
Almost exclusively, I use a diminutive of my first name.
Although René is the masculine of Renée, so you could also use it to sign fake letters written as if you were male. If you were so inclined.
I go by my first name.
I usually go by the short form of my first name.
At work, there are a few "Digital"s…some people call me “Analog” just to differentiate us.
Oddly, no one calls me D/a.
-D/a
Just be happy they’re not trying to convert you.
And for content, most people call me by the short form of my first name. Some people inadvertently call me by my last name in the mistaken impression that it’s my first name, and it annoys me.
So, I screwed up the vote… sorry about that! I meant to pick first and last name, but picked first and middle.
At work, I go by just my last name. No title. Though my partners usually know my first name, and I theirs, we work around the unsavory, unwashed masses, and none of us want them to know our first names, ever. Or any other personal information about us, for that matter.
Most friends and family call me by a diminutive form of my first name.
I go by several different names.
With my immediate family, my coworkers, and my niece’s mother, I use the first name on my birth certificate.
With the rest of my family, I’ve given up on them using that instead of the diminutive I used as a kid.
With most of my friends, I go by various nicknames (generally based on my online handles).
Middle name. I’ve never used my first name, even my childhood name was a form of my middle name.
In the poll, I picked middle name but actually it is a nickname formed of my middle name. If I ever get a phone call for my first name, then I know it’s a bill collector or other bad news.
Actually my grandma picked my name for me. She said (when I was a wee baby) “He’s no (first name), he’s (nickname of my middle name)”. And that was that. 
I go by my first name which many either don’t know how to pronounce or spell. I also have a few nicknames. I like most of them and like it when people call me by them.
I voted other, as I answer to either of two nicknames based on my long first name. My full first name is used on legal documents only.
I go by my nickname because my first name is like the Indian version of Brunhilde and even mah peepul have a hard time spitting it out. Thanks Mom and Dad!
I must say that I don’t get the American obsession with the concept of First Name, Middle Name and Last Name. I have three forenames and one surname and I go by the second of the forenames.
I usually go by my first initial.
I’m one of those people who do specifically prefer not to be called by a diminutive of my name…except if you just call me T.