A water filter: Go to a store and ask to try samples of water from your city through each of the types of filters. See which you like the taste of better; if any. Consider costs vs long term tastyness of water. It really depends on your city and the water quality. Some places have terrible tasting water; some don't. I have a reverse osmosis system.

Quantified self tracking devices. Basis seems coolest right now. RescueTime is valuable too...

A good showerhead.

A Musical instrument to play around on.

A sketch drawing pad; just in case - easier to have it than the want it when you don't have it.

Pets! (I think they improve happiness but I don't remember where I got that information from)

Garden plants - Lemon tree, herbs. Other fruity delicious things...