I used to do a nice country-ish version of Purple Rain--and did "Just Because" a lot---

I have played in a lot of different musical genre and make a point of trying to recycle as much material as I can-- pop tunes from the early teens to the thirties seem to be the most resiliant, you can usually do pretty well sticking in Ain't Misbehavin', All of Me, Five Foot Two, and that sort of thing at a folk gig without raising an eyebrow--Country and Western stuff probably whouldn't even count, because the musical line is so thin--

I've had a lot of luck with "I'll see you in my dreams" and "The Glory of Love" as well..

Contrary to what someone mentioned above, there are a lot of folk and traditional songs that do work really well in rock, pop, and jazz genres, the truth of the matter is that most genres have a lot of folk and tradtional music in their "songbooks'

St. James Infirmary seems like it works in almost every genre--