Engineer has been through a lot in recent years. Once a builder of teleporters and drones, he's decided to shift away from aggressive tools in favor of more supportive ones. While he still carries around his signature jackhammer for Chomper-immune sprinting, the Heavy Helper, Bullhorn Swarm, and Double Time boost pads are all new inventions aimed to better support his team.
One of the few things Engineer has kept close to him is the reliable Concrete Launcher which fires explosive concrete chunks that deal 36 damage on a direct hit and 10 splash damage. A minor upgrade this weapon's recieved comes in the form of concrete that bounces off of surfaces before detonation, allowing for tricky ricochets that can lead to off-the-wall vanquishes.
Like the Sonic Gernades and Proximity Sonic Mines of the past, the Bullhorn Swarm aims to stun those pesky plants with really loud sounds. Unlike the stunning megaphones of old, these ones will linger in the air until a target comes by. When this happens, all of them will home in on the unfortunate foe for quite the stunning result.
Improving off of the Bolt Blaster design, the Heavy Helper is a fully automated turret that no longer needs the Engineer to manualy shoot it! While active, this turret emits a powerful aura which increases the fire rate of any zombie standing within it by 25% while also replenishing ammo! If that doesn't count as helpful, then Engineer might have to think of a new name for this thing...
With the help of Engineer's new invention, zombies are able to effectively double their movement speed just by stepping on a single boost pad! The short speed boost Double Time provides allows the zombie team to quickly get back into the action after respawning. Plants can easily destroy the pad though. They were probably jealous of the fact that they can't make use of the Double Time's speed boost.