You can tune a guitar but you can't tuna fish.
One requires a tweetment and the other need an oinkment.
One goes quick and the other goes quack!
It didn't have any pickups
I didn't expose myself inside a guitar this morning.
A tuna, because the rest of them are crustaceans.
You can tuna piano, but you cant piano tuna!
You can tune the lawnmower and the owner's neighbors don't mind if you don't return the sax when you borrow it.
BA-NA-NA-NAAA!!!!! (to the tune of Beethoven's 5th symphony)