Guardian pet

Guardian pets are one of three types of pets that can be summoned/created.
 * They will enter into combat on their summoner's behalf, much as a combat pet will, but cannot be directly controlled. They react as a combat pet set on Aggressive and Follow.
 * They are generally summoned on a temporary basis, unlike combat pets or Small Pets.

Most guardian pets "share a cooldown" with other guardian pets of 1 minute.

Most non-consumable items (of all varieties) that generate guardian pets have a longer cooldown period than 1 minute. For these items, it is more descriptive to say that they force a global "guardian pet item" cooldown of 1 minute.

This means that while you may not summon a second guardian within that 1 minute, you may use each of your pet summoning items in turn. For instance, once you've waited a minute after using your Mithril Mechanical Dragonling, you can then use your Mechanical Dragonling trinket.

Engineering guardians
Many guardian pets are created by and for engineers.

Some engineered guardian pets are consumable items, and can be used only once per item:
 * Compact Harvest Reaper Kit
 * Gnomish Alarm-o-Bot
 * Gnomish Flame Turret

Other engineered guardian pets are reuseable. These generally take the form of trinkets. While these pet may be killed by damage, you simply wait for their cooldown and you can use them again. Their cooldowns range from 1/2 hour to one hour between uses.
 * Mechanical Dragonling
 * Gnomish Battle Chicken
 * Goblin Bomb Dispenser
 * Mithril Mechanical Dragonling
 * Arcanite Dragonling

Engineering pets scale with the Engineer's skill level, and their damage output increases. However, they have the same amount of hit points as the level they started as.

Guardian items
These are non-engineering items that summon Guardians:
 * Cleansed Timberling Heart (consumable, reward from Planting the Heart)
 * Glowing Cat Figurine (consumable, loot from Ghost Saber)
 * Expedition Flare (consumable,, requires reputation with the Cenarion Expedition)
 * Mechanical Yeti (quest reward in Winterspring)
 * Barov Peasant Caller (quest reward in Western Plaguelands)
 * Ancient Cornerstone Grimoire (loot from Onyxia)
 * Book of the Dead (loot from Balnazzar in Stratholme)
 * Defender of the Timbermaw (reputation reward from Timbermaw Hold)
 * Shard of Azzinoth (loot from Illidan Stormrage)
 * The Horseman's Blade (loot from The Headless Horseman)

Class abilities
Many of these guardians are summoned by talent abilities, while others are summoned by passive talents or regular abilities.
 * The Balance Druid level 15 talent Force of Nature summons three guardian treants.
 * Fire Elementals, Earth Elementals, and Storm Elementals summoned by Shamans are guardians unless the Shaman has the talent Primal Elementalist, which causes them instead to be controllable pets.
 * Warlocks can summon an Infernal, Darkglare, or a Demonic Tyrant as guardians, depending on the warlock's specialization.
 * The Demonology specialization for Warlocks is heavily based around rapidly summoning short-lived demonic guardian minions:
 * Hand of Gul'dan summons up to 3 Wild Imp minions, based on Soul Shards consumed.
 * Call Dreadstalkers summons 2 Dreadstalker minions.
 * The level 60 talent Summon Vilefiend summons a Vilefiend minion.
 * The level 90 talent Grimoire: Felguard summons a Felguard minion. Unlike the Felguard from Summon Felguard, this Felguard is an uncontrollable guardian minion.
 * The level 90 talent Inner Demons periodically summons the same Wild Imp minions that Hand of Gul'dan summons, and also has a chance to summon one of a number of other random demonic minions.
 * The level 100 talent Nether Portal summons random demonic minions every time the warlock spends Soul Shards while it is active.
 * Landing a killing blow with the damage from the level 30 talent Doom has a low chance to summon a Doomguard minion.
 * The PvP talents Call Felhunter, Call Observer, and Call Fel Lord all summon guardian minions.
 * Paladins can summon a Guardian of Ancient Kings.
 * Death Knights have a large variety of guardian pets available:
 * The Unholy ability Army of the Dead summons 8 ghoul guardians, and the Unholy ability Apocalypse summons up to 4 ghoul guardians depending on the number of Festering Wounds consumed.
 * The level 90 Blood talent Bloodworms randomly spawns short Bloodworm guardians.
 * The Blood ability Dancing Rune Weapon and level 100 Unholy talent Summon Gargoyle both summon guardians.
 * Beast Mastery Hunters can summon guardian animals with the level 15 talent Dire Beast, the level 100 talent Spitting Cobra, and as a random chance when casting Kill Command with the Azerite trait Dire Consequences.
 * The Windwalker Monk ability Storm, Earth, and Fire summons 2 guardian spirits, splitting the monk's damage between themself and the two uncontrollable spirits.