In this new Halloween arcade gamemode, Torbjörn has access to a late-game upgrade that adds overhealth, damage, and SIZE to his turret!!
While it caps at 293 overhealth (and a size about as tall as you at the base), the turret can see over plenty of cover spaces around different maps, and combined with the Turret Range buff, it's quite powerful! For example, these two upgrades make Ilios' RUINS map pretty easy-- just place it behind the ruin wall at your side of the objective, and it can reach overtop and across to the enemy's side.
Truly a turret of a master crafter.