The Chainsaw is the only equippable melee weapon in the game, unlocked at level 23. Unlike other chainsaws from Valve games, it does not use fuel and therefore never runs out of ammo. Its use on the battlefield is limited to support roles, because it cannot deal with more than one enemy at a time, and is limited to melee-range combat. However, it is rather effective at dealing damage to a single enemy and can conserve ammo when dealing with larger Swarm aliens.
A gasoline powered chainsaw with a horizontal blade.
- High, constant damage
- Infinite ammo
- No reload
- Must be in melee range
- Weak against multiple attacking aliens
- Attacking slows the marine down to a walk
- Deals large amounts of friendly fire
- Not affected by the Power Fist OR the Damage Amplifier aura
- Cannot destroy explosive barrels
- A good strategy for using the Chainsaw is to identify places where its weaknesses will not be as pronounced. A stage like Deima Surface Bridge or Timor Station that requires lots of fighting while moving and features multiple possible routes of attack is not a good place for the Chainsaw. In contrast, the Cargo Elevator is a more acceptable place to use it: the area to defend is a small box that the marines must hold, allowing the Chainsaw's movement restriction and lack of range to be less of an issue.
- On the lower difficulty levels, the Chainsaw can work as a primary weapon, especially with Jaeger or Vegas. On Hard/Insane the risks begin to outweigh the benefits.
- The Swarm can manage to work behind you (even in corners or against walls) and sneak in repeated hits. It is wise to have a Technician on board while using the Chainsaw to prevent this.
- Swarm can time their lunge attacks towards you in time, so it is wise to keep moving towards the Aliens direction and funnel them in towards you when possible.
- The Chainsaw can work as a substitute for a Welder: since it deals high damage without expending ammunition, it is an excellent choice for breaking down a welded door if a welder is not available. It can also destroy boulders like the Mining Laser.
- When fighting Shieldbugs, a good tactic is to attack it while another marine stuns it with the Tesla Cannon or freezes it with Freeze Grenades.
- When shredding through locked doors that are also attacked by aliens from the other side, the door will likely fall on the Swarm's side, killing them.
- May kill airborne Parasites if aimed well.