Although it will surely change, at my current count of 260 videos in my Favorites list, the one with the least views (73) is
December 2010 Overnight 1 which I looked up recently to find Billy Joe Walker, Jr.'s “Treehouse”
My most viewed (12,426,414) is
What about yours?
Most:
Spoony’s Final Fantasy VIII Review Part 1 Views: 430,495
Least:
Nostalgia Critic “Care Bears 2” Part Two Views: 2,269
I excluded private videos of mine that I favorited to view on Roku.
Most: Bed Intruder Song, 69,156,101 views.
Least: Richard Feynman Interview #6, 27,279 views.
Impressive! I just discovered “Bed Intruder” last month so one of those views is mine! 
This is going to be hard to beat, I suspect. Somewhere just recently I saw the statement on some clip that it was the most viewed, but I can’t remember what it was or how many views it had. Over 100,000,000 maybe?
This list may not be THE record setters, but I can feel comfortable knowing that none of them is (or will be) on my Favorites list.
However, if one of them is on YOUR list, jump out and take the lead in the Most Viewed rankings.
Did you guys notice that youtube’s “Sort by most viewed” is seriously broken?
Anyway, my least watched favorite is Sexual Biology Series: Part 4c Intersexual selection, part of a fascinating series of videos by the always interesting LithodidMan, who by all rights should have at least 10 times as many subscribers.
Most watched: Charlie the Unicorn (55 million views and counting!).