Previous Manager: Mobbsy
Current Manager: Dave
OTL (Manager’s Manager): Robyn
Centre Manager: Gary
CEO of the company: POS (Seriously, it’s what he signs his name off as in the company-wide emails)
Swiss Boss:
by his firstname.
German Boss:
Boss, Bossman, Michael, Michael-1 (which is what the email system calls him).
Same behind their backs. We have several Michaels in the team, so if someone says “I spoke with Michael” they’re often interrupted with “Michael E, Michael J or Michael-1?”
Heh. We have two Michaels here, too – one of the is the CEO. So, if there is any chance of confusion, we say “Big Michael” or “Little Michael” as appropriate (helps that CEO is… of substantial girth, and the other Michael not so much 
) This is only “behind their backs,” so to speak, of course – no confusion when talking to one!
I’ve called all my immediate supervisors by their first names. When I started out working for a government department in the '80s, the managers were always Mr.-- or Mrs. – to start off with. Almost like with schoolteachers. Even now, working for myself, I hesitate before calling a manager who represents a corporate client by their first name – but I do, because it’s expected and what everyone does these days.
I have two bosses*, both of the same rank, so I usually call them “Captain” when I talk to them directly. When I’m talking about them, I usually call them by their last name to avoid confusion. I get along well with both of them so I don’t have any evil nicknames for them**.
*Up until today, that is. One of my bosses appears to have lost his job.
**But in the past, I’ve had less admired superiors, who have had nicknames like the Midget, Big Head Ed, El Lobo, Crazy Krazinsky, Stormin’ Norman, Monkey Boy, Dorothy, Mad Dog, Brain Damage, Frank the Tank, the Idiot, Bug Eyes, the Walrus, Snoopy, Little Debbie, Bullethead, the Ripper, and Liver Spots.
I remembered one more. We had a boss we all called Mike. Which always confused him because his first name wasn’t Michael.
But his last name was Hunt.
That asshole…
Oh wait, I am the boss…
My immediate supervisor was Firstname until I knew him well, and then he became Mr Surname most of the time, Firstname if I’m asking him a serious question (IOW - “Could you look over these financial reports, Firstname? I think we have a problem on page 5” vs. “Coffee, Mr Surname?” or “Coffee, Mr S?”). He called me by my first name until he knew me well, and then he switched to Mrs I(nitial). Now that I’ve changed my name and marital status, he’s back to calling me by my first name, hehe. It’s taking everyone some time to get used to the new name.
Our mutual boss is Firstname. I called him Mr Surname once on my first day and was immediately and firmly corrected.
I’ve been calling our boss’s boss (who is stationed at head office) Mr Surname for five years - he just picked up on it about two weeks ago and corrected me, insisting I call him by his first name. I have trouble doing this because he’s older than me and I don’t know him well.
I call a lot of people Mr _____ or M/s _____, especially friends (Hi Mrs. K!). It’s not special treatment reserved for bosses.
Hi Ms T! (ooh, does that sound weird or what!)
I’ve always known my bosses by their first names. The only time I ever used “Mr/Mrs” was when I was in school (and, of course, Cazzle).
It used to be first name, but I recently bought the company, so now it’s “the Boss.” As in “Don’t tell the Boss I’m gonna be late cuz I’m hungover.”
First Name.
I have two bosses in my very small, very informal office.
For both of them I use first names or diminutives. Boss #2 and I call each other Bitch too. We tend to use silly terms of endearment with each other a lot (my dear, sugar, pumpkin, babe), peppered with insults (slut, bitch, freak) and overly formal terms (sir, ma’am, Mr/Miss Firstname).
I love both of my bosses, so I don’t use insulting names behind their backs.
I call my immediate supervisor by her first name, as do the rest of her immediate subordinates. We do this because we are all friendly with her. The head boss, on the other hand, is Ms. Lastname. No one likes her that much, as far as I can tell.
I call my boss “Fearless Leader” much of the time. However, on specific projects that aren’t going as well as hoped, he often becomes “Fearful Leader”.
If I’m up for a review or a raise, he becomes “Oh Kind and Generous Leader”
In meetings, he’s always called by FirstName. There are literally 88 people in our company with his last name, but he’s the only one with that first name.
Eli
Mike, or “Big Man” to his face. (He’s 6’6", and I’m 5’4")
Many, many colorful things while out of earshot. It didn’t start out that way. I used to love the guy. But he got the “Stepford Executive Infection” and now I barely tolerate him.
So, this leads me to tell you that because of that, and because of my need to quit making someone else look good, as of the 23rd, I’ll be calling my boss, “ME!”
My partners, however (husband and longtime friend) will just have to be content with whatever strikes me that day. 
I never worked at a place where everyone didn’t use first names with everyone or anyone else. In nearly nine years of working here, I’ve never once heard the words “Mr.” or “Ms.”.
I think we’re all Firstname to each other, unless we’re speaking in front of numbers of students, and then it’s Professor X or Dr X.
Luckily, I work in a collective where no one is boss over anybody else. We all call each other by our first names or nicknames, both in front of and behind one another… Makes for a pretty good atmosphere.
First name. If I’m referring to him to others (in his presence or not), I’ll sometimes call him El Jefe, which virtually no one I work with gets.
Many of us refer to him (in his presence or not) as “The Big Guy,” which is a somewhat of a joke, because he is a very slightly-built man who favors bow ties. (Not that there’s anything wrong with bow ties…but they don’t seem to fit with the image conjured up by “Big Guy.”)
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Immediate supervisor is Firstname. And the doctors I work with are all “Dr. Lastname.”
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Behind backs? I refer to one of the doctors as “Dr. Snape.”