My own current range includes a lot of the usual stuff, but I list a few here that I never (or rarely) hear anyone else doing:

Where known, I give the (author) or (ex-artist) but otherwise may be trad or I just don't know.....

Farewell to Whisky
My Father (Judy Collins)
My Rainbow Race (Pete Seeger)
Carolina in My Mind (James Taylor)
Strong Women Rule Us All (ex-Dick Gaughan)
Consummation (Claire Hamill)
Too Late for Prayin (Gordon Lightfoot)
The Hiring Fair (Ralph McTell)
If It Be Your Will (Leonard Cohen)
Fotheringay (Sandy Denny)
Making Up The Miles (Kieran Halpin)
Anna My Love (Harvey Andrews)
The Lancashire Lads (ex-Mike Harding)

I also play a few self-penned ditties and, when my son is around, we duet on:
Crazy Man Michael (Fairport) and Ride On (Christy Moore) (my son who plays a cool counterpoint to my rhythm section & vocals) and
Samba Pa Ti (Carlos Santana) (my son plays lead - goes down a storm!)

Got some good suggestions from others above, thanks, I'll have to start digging around again. Always good to find new stuff.