There are a handful of songs that one immediately thinks of the minute you see a guitar. Odds are you already know which ones they are, but I'll go ahead and list them, just in case.
Let's say your friend tells you that they haven't played guitar in years but used to mess around a bit back in (insert the applicable era of your youth here). The second they start to strum, it wouldn't be shocking if the first song they picked was Smoke on the Water. Or, let's say they claim to be quite proficient at guitar. In that instance, they'll probably opt for Stairway to Heaven or Freebird. And then, of course, if you're from Gen Z, they'll probably ask, "what's a guitar" before they show you their rap video.
Even though Freebird has become a cliche song for solos on guitar, it's still a novel choice for other instruments. In the video linked above, you can check out the YouTuber Will Wilde performing the solo on harmonica.