One tune was stuck in my head most of the time while hiking the PCT this year. It's called Pachelbel Canon.
Its rhythm seemed to match the rhythm of walking perfectly. It's a tune that if you don't know exactly how it goes, you know enough of it to make up all kinds of variations. It's a never ending tune. It goes round and round again until you are driven mad.
The other main tune that got stuck in my head was Leader of the Band. I think the rhythm is similar to Pachelbel Canon.
I think the proportions were about 70% Pachelbel Canon, 25% Leader of the Band and 5% assorted Irish Traditional tunes.