Flamarang

The boomerang leaves your hand fast and holds that speed for a fraction of a second, then bleeds off and curls back. The moment it starts slowing it changes character completely: it stops caring about walls and stops caring about how many things it has already hit. Standing so an enemy sits right at the far end of the arc is the whole trick, because the weapon will grind into it repeatedly while it turns around, and it will clip anything tucked just inside a block wall.

Anything that raises melee speed throws it further, since the arc is a function of how fast it left your hand. Water and honey drag on it and cut the arc short, so an underwater fight hands you a much shorter weapon than the same fight on dry land. It also expires on a timer and vanishes if you outrun it, which matters if you throw and then immediately fly off.

The burn it applies is brief but it goes back on with every pass, so it holds well on something that is not moving. Queen Bee while she hovers and spits out her swarm is the best case: the boomerang keeps ticking her down and shreds the bees drifting at you on each leg of the trip. It also lights up everything it passes, which makes it a passable scout in unlit caves.