Percy Grainger was something of an iconoclast. While the music world around him was deep into atonality and serialism, he was writing music based on folk song, but in a way unlike anyone else. He was a monumental pianist, so naturally most of his works at some point ended up arranged for piano (for many of his pieces there are several different arrangements, all by Grainger). Luckily for us, there is a ton of this music on youtube.
My first suggestion is his classic “Molly on the Shore.” It is probably best known in the band arrangement, but there is little lost in the piano version.
“Shepherd’s Hey,” like Molly, is an adaptation of a folk song. This one is fast and fun.
The “Gum-Sucker’s March” is a personal favorite of mine. It is a sort of collage of tunes; the second melody is a quote from his “Colonial Song,” and the third melody is from “The Widow’s Party,” which sadly isn’t on youtube in piano form, but there is a band version.
Without a single doubt, the funnest piano piece, probably ever, is Grainger’s “In Dahomey (Cakewalk-Smasher).” With the sheet music we get to see all of Grainger’s blue-eyed English (he was something of an Aryan supremacist): Half short, sharp chippy and dead rhythmic, like a brass band, and (my favorite) strumpy banjo-like. There are more ossia lines than should be allowed, and several places for cuts, and best of all tons of loud glisses, as well as trombone sounds.
Try listening to this stuff and not enjoy yourself. You’ll have a hard time.