There is just something about ukuleles. They just seem to attract positive vibes.
In general, short scale nylon stringed fretted instruments just radiate a "cheerful" demeanor.
My most cheerful sounding instrument currently is a requinto I found at Goodwill for $14.
It is a small variant of a classical guitar, widely used in Mexican music. Mine is tuned to G, many are tuned a whole step higher to A.
I strum it and just smile.