Mine would be the Hal an Tow. I used to "do" the Hal an Tow as a teenager and I would take it because I could pass on not only the song but the stories behind it and the pageantry of it.
It is not necessarily my favourite song (as if that were possible!) but it reminds me of being young and looking forward to long summers.
And Scabby Doug has my other one so that's all right then!