Not exactly a weapon, but the Fenris-class Assault Drone might be worth mentioning.
You can get it at Tarkus in the Stellar Tether mission, after defeating Tam.
As a tech specialist with the attack drone perk it replaces your attack drone, and deals more damage. (At the cost of less shield capacity)
If you don't have this perk you can still acquire it, but as a damaged unit that's much weaker, and only has a 70% chance to attack the enemy.