The Stim Pistol is a veritable game-changer in World War Z, and essential for surviving on the higher difficulty levels. Based on the 2013 movie, and the 2006 novel, World War Z features some of the most satisfying zombie-killing co-op action this side of Left 4 Dead. On early difficulties, reasonably skilled teams can blast their way through the co-op missions with little trouble, but the excitement truly ramps up when the difficulty gets cranked to Hard and above.
On higher difficulties, the zombies get a lot tougher, and an unprepared squad can easily get overrun unless they communicate, strategize, and mix up their classes to maximize their tactical potential. There are six classes to choose from; while they generally start off pretty similarly, leveling up past level 15 or so truly reveals their unique specialties. One of the most useful classes in the game is the Medic, who has access to the Stim Pistol, one of the most useful items in the game.
From the outset, the Medic starts out with a free Medkit (all other Medkits must be found in the field) and the Stim Pistol, the use of which can be a bit confusing to new players. With upgrades earned from leveling up, the Medic is possibly the absolute most useful class in World War Z.
Every class starts with a different secondary item mapped to the L1 or left bumper button. Most are destructive, like the Frag Grenade, C4, or Stun Gun (which is essentially a unique version of a grenade); however, the Fixer class carries a Supply Bag which drops explosive ammo for allies to pick up, and the Medic carries a Stim Pistol. The Stim Pistol can be confusing to use, and its usefulness isn't completely articulated within the game itself. Tapping the L1 button causes the Medic to stick themselves with the Stim Pistol, giving them a temporary shield which really helps out in a pinch. To use it on an ally, the Medic must hold the button down until the targeted ally is surrounded by a faintly glowing outline, then release the button.
Using the Stim Pistol can be a lifesaver when used correctly. When allies are low on health, a temporary buffer can buy time to escape or kill off an encroaching group of zombies. Building off this, the Medic class can be upgraded so that using the Stim Pistol on an ally gives temporary health to the user, as well. Another upgrade allows Medics to gain health when healing others with Medkits. With these skills, a Medic can effectively rescue allies from certain death even while being surrounded by zombies. It's still easy to get overrun, but having a skilled Medic in the mix can be a serious game-changer, especially on tougher encounters in the harder difficulty settings.