Or bridge out a bit in terms of stringed instruments. I already have and acoustic bass and a Ukulele, plus a while back I added a mandolin and just 2 weeks back a banjo (ngd for the last too incoming as soon as I take pictures...which could be tomorrow...could).
All are really fun to play, especially the ukulele and the banjo. Great for when you want to do some acoustic stuff.
Also it can give you new ideas for your playing. Most effect here I already feel from the banjo, it makes you play differently and when you translate that to your guitar it can give a nice flavour.
Guitar banjos are also really nice.