A really easy to learn and quick result instrument is the bowed psaltery.
It is a string instrument in the family of harp, zither and dulcimer, though it is not plucked. It has a wonderful etherical sound. If you know already some music it takes about 5 minutes to play your first tune, if not it takes about half an hour.
I started playing with two bows after a while, to create a second voice according with the melody. It doesn't take that much of your time to learn and you get a lot in return.
It is like a meditation to me.
I got mine at http://www.unicornstrings.com
, but a search on google learns that there are other providers available as well.