Broken Hero's Sword

The Broken Hero's Sword is a rare item that drops off of various bloons. When equipped, it gives the tower a attack speed boost. It also makes the tower pop off 2 more layers than usual. The downside is that the tower now has to attack with a melee weapon. The 4/4 Terraria Monkey also has the broken hero's sword's boosts. It has a 0.1% chance to be dropped.

List of bloons that drop it
Z.O.M.G.

D.D.T.

T.O.M., F.R.E.D. and H.A.R.R.Y.

A.N.C.I.E.N.T. and G.R.A.V.I.T.Y.

S.U.P.E.R.B.

B.L.I.T.Z.

Super Bloon

Hyper Bloon

E.V.O.L.V.E.

Trivia
Three of this item can be crafted together to make the Terra Blade, an Epic item that upgrades a 4/2 or 2/4 Terraria Monkey to 4/4.