What is your minimal requirement for someone to call themselves guitarist?

Have picked up a guitar, played a note and smiled.

I can't remember who wrote it, but there's a short essay by a Japanese noise rock artist (maybe Agata from Melt Banana?) on 'How to be a guitarist' and it basically says 'Get a guitar. Tune it if you like but this isn't necessary.' So, yeah: that's about where I'm at on the question.

If you ever try, or even have tried, good enough.

Don't worry about labels - stick with the hobby, it's good for ya.

Don't really think there's a minimum - sure maybe you ought to have picked up a guitar but there's no minimum proficiency for creative arts.

yeah, pretty much what blackstrat said. If someone can pick up a guitar, and play it!

Answer is probably different if you're trying to hire a guitarist for something or if you're trying to decide whether some random person is a guitarist.

Said person has a guitar and is playing it. That's it.

Anyone can call themselves a guitarist but there are only half a dozen Certified Guitar Players.

They should be able to play at least 1 song.

Just try. Good, bad, in the middle. Play it and love it.

I started playing when I was 10 years old in 1966. I have been a guitarist the entire time. I am slightly better now, though.

Trying to define this or answer this question is an exercise in futility.

If you feel comfortable calling yourself a guitarist, poof-- you are one, regardless of what anyone else says. I wish I'd deeply bought into this decades sooner. Comparisons are odious. Rock on.