I have two good Leon stories.
Saw him 5/16/93 at Herman's Hideaway in Denver. Unbeknownst to me, he had a little schtick he tended to do in concert where he had the stage lights out and took out a flashlight to scan the faces of the audience. While he was doing this, I happened to have a penlight in hand for my own nefarious reasons, so when he got to me with his flashlight I pointed mine at him and switched it on. He burst out laughing and said "man comes prepared."
Saw him again at Swallow Hill on 4/15/11, and my friend Laurie and I snuck backstage to greet him. He was very friendly. I asked him about his whistling, and if he had ever heard of jazz whistler Ron McCroby. He had not, and I suspect many here on QQ have not either. I gave Leon a tape (yes, cassette) I had in my car so he could check him out. He was very thankful for it.
Leon warmed up for Tom Waits on a full tour in the fall of 1978. I so wish I had seen that tour! It was just a little too early for me.
RIP Leon. Great music and great friendly energy!