Voigtlander 40mm E
When I had my Sony A7 I got my first manual Voigtlander lens after watching a video on YouTube about it's quality and character.
Once I started taking photos with it: I was hooked. I loved the manual experience and how it slowed me down when taking photos.
This set me off on quite the rabbit hole with photography which eventually led me to buying a used Leica M10.