[JonPR]

For me, it would be guitar instrumental tunes, not "songs" as such. My favourite songs were always pretty simple ones, at least at the beginning (Dylan, blues, folk, etc).
My source of accomplishment in the early days was fingerstyle guitar - e.g., getting Angie worked out, and various other tracks on Bert Jansch's debut LP. Also ragtime pieces, mostly from Stefan Grossman records (Dallas Rag, Delia, etc). And of course, Dylan's fancier guitar tunes like Don't Think Twice and Girl of the North Country. And Donovan. (Hey it was the 1960s...)

I.e., for me, there was a distinction between "songs" (lyrics, melody, chord sequence) and "guitar technique", which only applied to certain specific songs or instrumentals. I was into songwriting as much as guitar playing, but learning those songs wasn't hard at all. It was the fingerstyle guitar that presented the exciting and satisfying challenges.

I still wouldn't say the emotion I had at the time was "wow", or amazement at how well I'd done. Naturally I'd be pleased with myself, but I'd be moving on to something else, just enjoying the whole process.