First name, (Mr.) last name, or first half of my (rare) middle name, as those are the only names by which I am known to anyone in this solar system. There are no common diminutives to my first name.
In a doctor’s office? Only my real name, first, last or both - is that three? In real life I go by an assumed name, which has three possible diminutives, so that’s another four. People have occasionally attempted to address me by my middle name, but I wouldn’t automatically answer to it unless there was no-one else there they could realistically be talking to. Also two screen names, either of which would attract my attention if shouted in the street.
I presume we’re not including pet names used by family members/SOs.
So… ten possible names, of which three would attract my attention in a doctor’s waiting room.
Oh, there are diminutives of my real name. If I heard one of those in the street I’d probably run, since only people I went to school with ever called me by those. Another three there.
First name, Ms/Miss Last name or First + Last. The doctors around here frequently have a spot on their forms for you to specify a different name you want to go by if you’d like, but I never do. The only people who ever call me anything other than my legal first name are my parents.
My first name is uncommon, so if I heard it or any variation, I’d respond. Also, my nickname, Crackrat, I respond to, though that doesn’t get used as much as it was in high school.
That said, if I’m in a conversation with someone, I will respond to them if I know they’re talking to me, even when they use the wrong name. There have been many occasions where a friend calls me by another friend’s name. My best friend and roommate in college and I were so often mixed up by other people that I once responded to him calling me by his name.