So many, especially the very early ones.

Top favorite is probably "10 Degrees and Getting Colder". A perfect finely etched picture with just a few strokes.   You can see the guy by the side of the road and feel it getting colder by Boulder Dam as the sun goes down.

Other great Lightfoot songs, most of which have been already mentioned:

Early Morning Rain
Did She Mention My Name?
Ribbon of Darkness
Long Way Back Home
Edmund Fitzgerald
For Lovin' Me
I'm Not Sayin'
Canadian Railroad Trilogy
The Way I Feel
If You Could Read My Mind--even the soupy strings work--somehow.
Sundown