Area of special competence
The office where I used to work had a dispenser that provided steaming hot water suitable for making tea.  It was really handy, and I felt its lack when I didn't have access to it any more--and had to resort to making hot water in a tea kettle.

I make hot water several times a day, in all different amounts, depending on whether I'm making a mug of tea or a whole pot, or whether I'm making cocoa instead, and whether Jackie wants hot water for something at the same time.  Over the past few months, I've become really quite good at filling the kettle with just the right amount of water for whatever we're planning to do with it.  (No point in spending energy heating up water that will just sit in the kettle or get poured down the drain, after all.)

The thing that surprises me is how pleased I am with this utterly trivial skill.