The Boomerang is an item used for defense and as a tool in Adventure Mode. Similar to the Hookshot, the Boomerang can also pick up dropped items when thrown.
Boomerang Hotbar Icon
Inside and outside of battle, the Boomerang can be thrown at any mob (passive or aggressive) to stun them.
As a tool, the Boomerang can be thrown to activate levers, wooden pressure plates, and buttons. It can also pass through Clip Blocks. When thrown, the in-hand sprite will change to an outline of the Boomerang until its return. It can also be used while hanging from a Hookshot.
There's a key across this lava lake, way out of my reach...
Aha! It can be easily obtained by throwing the Boomerang