When I was growing up and learning to play the guitar a bit I learned to play some rhythm and flatpick some from my grandfather. I absorbed a ton of information about music and acoustic guitars over the years from just being around him and listening to him talk so enthusiastically about the subjects, and really, I had no idea just how much I'd picked up until many years later.
The first tune that I ever learned to flatpick was The Wildwood Flower, and of course that is the perfect simple but memorable tune to be a first one for a flatpicker, or a rhythm guitar piece. I might have learned that one first on rhythm, but I doubt it.
The second song that I learned was The Turkey In The Straw, and that's another well known tune from the fiddle tune melodies of Appalachian or Scotch Irish music. I'll always remember that my grandfather taught me one arrangement of it, but when we'd trade off playing, he'd play a different version of it. He wouldn't teach me HIS version either!!! He said something like,
"No, that one is mine, you can make up your own though."
Well, It's a great song to learn to play, and everyone under the American sun has heard this song at one point or another. It's most often heard as the song that the ice cream trucks patrolling neighbourhoods play as they creep through selling their wares. Let's hear it, shall we?
You really can't beat the version above - that's a super trio of musicians there, and they play a splendid and true to the original melody rendition of it. But let me find a much simpler version of the tune for anyone that is interested in learning the song on guitar with tab.
Now the link above is great because it's up the neck instead of in the first or open position. When you're a youngster learning guitar - you might think that playing in the open position is less technically challenging - but to an electric guitarist - playing open position numbers on acoustic is more challenging - that's the perspective that I lacked when I was younger.
And the link above here is another one up the neck - learn the neck my friends, and the best way to do that is with a single tune moving it to different positions and in different keys.
Are you more comfortable reading music? Well the above link is for you.
I hope that this has been useful to you.