I guess these first three are kind of limited scope improvents.

Fountain pens. Got me writing notes for work which has helped me stay more organized and on the ball and able to remember more. And with the right pen it makes note taking enjoyable.

Cast iron skillets have improved my enjoyment of cooking.

Portable jump starter has saved the day multiple times since I got it (me, friends, etc)

ADHD diagnosis late in life prompted by career-limiting struggles with a type-A boss. The diagnosis explained so many things about me, my behavior, my struggles in work and relationships, my self image, etc. Therapy helped develop better coping mechanisms and the meds help a lot with focus and motivation. All told, things are better with relationships and other areas of life, I turned around the boss's opinion and got my career back on track.