About any fiddle tune. Even the death dirge fiddle pieces are a lot happier then classical "expression"

A good book with many good tunes (with a nice range of skill level) and in it comes in many volumes - is called (Fiddlers) Fake Book,   I have 2 different volumes of it. each has about 1,000 songs.

I don't know your skill level, but there is a basic fiddle book series called "The American Fiddle Method" which has very simple pieces in it that are easy to add your own expressions to. Very good basic slides, trills and double stops towards the end of book 1.

Arrons Boat Song, Bonapart's Retreat, Stinky's Blues, Country Waltz. all fun to play. All in very simple form but can get very complicated if you wish them to.