Kalimbas are cool. Cheap and they sound lovely like a music box even if you don't know what you are doing. The sound is so nice that my cat has several times fallen asleep right beside me while I've played
There are a bunch of instruments locked into a scale like the kalimba so you can never play a 'bad' note. I've got a tongue drum, some xylophones, and a ocarina for my kids to eventually start playing which are all like that