Tamron AD-2 SP 35~80/2.8~3.8 -- has a unique feel both optically and mechanically. It has a long, long focus throw that includes the zooming function! The bokeh has a unique, pleasingly granular feel to it - not buttery (at least mine did) and a color palette that renders warm and treats reds nicely. I've read this was a well-regarded, professional quality lens in the 80's.
All this being said for many years I decided to take this particular lens for a walk not so much to achieve an expected result but more for the experience of using the lens (although the end-product was always worth the time).
Alas, in a fit of LBA guilt, I foolishly sold all my Adaptall lenses and adapters to KEH one Saturday when they came to town.