Not talking about links or big site migrations. I mean something small you did in an afternoon that actually moved rankings.
Mine: I rewrote the title tags on 12 product category pages to match the exact phrasing people use in search (took it from GSC queries) instead of our internal category names. Avg position went from ~14 to ~7 in about 5 weeks. Felt stupid that we hadn’t done it earlier.
Fixing the heading order on our templates. Every product page went H1 straight to H4 because the theme styled H4 the way the designer liked. We switched it to proper H2/H3 and changed the CSS instead.
Can’t prove it was only that, but long-tail rankings went up across the board a few weeks later.
Internal links from the old posts that already had traffic to the new pages. Nothing fancy, 3-4 contextual links per new article. New posts got indexed in days instead of weeks and started ranking a lot faster.