Some of my favorites:
MD-80/90 (seats appear to be a little wider that the narrowbody Boeing fare.)
767-300 -- Not bad, but Delta seems to put the headphone jack and controls in the worst possible place!
Thumbs down: 757 (exit row no recline sardine-can seating)
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AlphaSigOU
Causa latet vis est notissima - the cause is hidden, the results are well-known.