Dragon's Tooth sword (DX)

The Dragon's Tooth Sword is a weapon consisting of a nanotechnologically created blade, which is dynamically 'forged' on command into a non-eutactic solid. Nanoscale whetting devices ensure that the blade is both unbreakable and lethally sharp. It was developed in VersaLife's Hong Kong laboratories and was used to help start a war between two prominent Triads.

The DTS is found in the secret compartment in Maggie Chow's apartment. Make sure to take out the MJ-12 troops in there before you try and grab it, because it takes a while for the case holding it to be unlocked

Tactics
The DTS is the most powerful melee weapon, bar none. It can kill most troopers in one hit, and down a MJ-12 Commando in two. If your melee skill is upgraded at all, it can kill a Commando in one swipe. It can also make short work of monsters as well. Unlike other melee weapons, it can destroy any type of Supply Crate in one hit, making it useful even if your character build don't specialize in melee weapons.

It's also effective against doors in Hong Kong and the Submarine Pen. This is a great way to conserve LAMs and GEP Gun ammo, especially in the sub pen.