In Quake 4, a Grunt is a man-sized, humanoid creature with sharp teeth, 3 eyes, and green canisters along its arms and back. The Grunt has a more ape-like build and alien facial structure compared to most other Strogg, who are more human-like in appearance.
Grunts usually attack with melee attacks, either by punching or pouncing at a target from more than a dozen feet away. Grunts can also occasionally attack distant targets with a shoulder-mounted rotary Machine Gun, but they rarely do this, instead preferring to focus exclusively on charging at the player for melee combat. They could be considered Quake 4's version of the Mutant and Enforcer combination.
When damaged, Grunts will often "frenzy"; injecting stroyent into their body from the green canisters lining their arms and back. This gives them a modest health boost as well as increasing the damage done by their melee attacks. However, they must stand still for a second or two while frenzying, which gives the player a short opportunity to blast them while they're unable to move or attack. When they frenzy, they roar, pound the ground, and have glowing green features on their body. Including their "eyes".
Grunts appear in the first level, and are the second-most commonly encountered enemies throughout the game next to the "cannon fodder" Strogg such as the Guards and the Tactical Strogg. Grunts are usually encountered one at a time, and they tend to attack abruptly from behind open doors or around corners. They are used in much the same way that Imps are in Quake 4's engine relative Doom 3.
They are slowly replaced by the tougher Berserkers as the game goes on, up to the point that Berserkers quickly surpass Grunts as the most commonly encountered melee-using enemy.
- Grunts are easy to take down if you keep your distance between you and them and start shooting them quickly as soon as they appear. They will charge you on sight, meaning it is a good idea to strafe backwards while pelting it with your own weapons. The Machine Gun and Shotgun can quickly kill one, especially if you aim for its large head (on Normal difficulty it typically takes 10-20 Machine Gun bullets or 2 Shotgun blasts to kill a Grunt). Grunts can pounce at you from a decent distance, so be ready to strafe at a moment's notice. Don't worry about their machine guns, as they rarely use them, and also the bullets are so weak they'll merely tickle you.
- At close to medium range, the easiest way to kill one is to run up in its face and blast it with two shots from the shotgun. If all the bullets connect, the second shot should be an instant kill. Grunts will stop charging and pause for a second to "frenzy" (inject stroyent from the canisters on their body) after taking a certain amount of damage, during which they become vulnerable to damage. This is very useful, as you can stun a Grunt by causing it to frenzy with a single shotgun blast, giving you time to kill it with a second blast. If you don't have the shotgun, keep feeding it with machine gun will have similar effect.
- When encountered alongside other enemies, the Grunt should be taken out first, as it tends to rush you as soon as it sees you. Try to backtrack and lure it into an empty hall so that you can completely focus on it. If you are ambushed or encountered them in point blank range, remember to keep a distance, don't let them get too close. You can, however, kill it quickly before taking too much damage.
- After the player is stroggified, Grunts become noticeably easier to kill, as the player's significantly increased speed allows them to outrun Grunts while backpedaling and firing at them.
- In escort situations, Grunts can easily kill your teammate and fail your mission if you let them get close. Shoot them as soon as possible when spotted, but if you see Berserkers around, deal with them first, then the Grunts. This is not common until the player is stroggified.
- The grunt may be a reference to the DC Comics character Bane, as he uses an experimental steroid to greatly increase his strength and stamina.
- It is possible, although very unlikely, that the Grunt was based on the Enforcer enemy from Quake II.
- More powerful than the Guard, but less powerful than the Berserker and Gunner, the Enforcer and Grunt both wield a machinegun for ranged combat (the former as a hand replacement, the latter on its shoulder), and will aggressively melee attack any enemies who happen to be close by.
- However, one of many differences between the two creatures is that the Enforcer is a lot more liberal in the use of its machinegun, whereas the Grunt prefers to close the distance quickly and maul enemies to death at close range. Both are burly creatures compared to the Strogg Guards, and both are quite common in the early stages of their respective games, although the Grunt appears to be more solitary than the Enforcer, which can sometimes be found in groups of two or three at a time.