Interesting topic starter! I'll add some of my favs thru the years...not necessarily in order:
Black Queen: S.Stills
To My Friend: Leslie West
Vaseline Machine Gun: Leo Kottke
Classical Gas
Bad Weather: Poco (I'm a sucker for 12-strings, OK?)
Agreed Nickel Creek stands out as true musicians who play music for the love of it! Their 1st (?) video on CMT was "When You Come Back Down", I believe the title was. What a haunting melody....great instrumentation and a stellar arrangement, IMHO.