While not all professions in GW2 have built-in "pet" skills, any profession can use summons that are triggered by equipment. What differentiates these summons aside from visual appearance? E.g., do some of them grant boons or conditions? Do they have notably different DPS or health? Or are they all essentially Generic Summon A, Generic Summon B, etc.?
I believe most or all such summons are triggered by Runes and Sigils. (Rock Dog, Parrot, Fleshreaver, Attack Bird, etc)