There are level 30 Earrings, Shields, Belts and Mantles that all trigger on Latent Effects. These all correspond with a job.
All of them activate via Subjob. Nothing else will trigger these to activate, NOT main job, ONLY subjob.
The newest jobs (Blu, Cor, Pup) do not have these items (as of 7/27/06).
Subjob: Bard - Singer's (Earring, Mantle, Shield, Song Belt) Subjob: Beastmaster - Trimmer's (Earring, Mantle, Aspis, Pick Belt) Subjob: Black Mage - Wizard's (Earring, Mantle, Shield, Staff Belt) Subjob: Dark Knight - Killer (Earring, Mantle, Targe, Scythe Belt) Subjob: Dragoon - Wyvern (Earring, Mantle, Targe, Lance Belt) Subjob: Monk - Wrestler's (Earring, Mantle, Aspis, Cestus Belt) Subjob: Ninja - Genin (Earring, Mantle, Aspis, Sarashi) Subjob: Paladin - Esquire's (Earring, Mantle, Targe, Shield Belt) Subjob: Ranger - Beater's (Earring, Mantle, Aspis, Gun Belt) Subjob: Red Mage - Warlock's (Earring, Mantle, Shield, Rapier Belt) Subjob: Samurai - Ashigaru (Earring, Mantle, Targe, Katana Obi) Subjob: Summoner - Magician's (Earring, Mantle, Shield, Avatar Belt) Subjob: Thief - Pilferer's (Earring, Mantle, Aspis, Dagger Belt) Subjob: Warrior - Mercenary's (Earring, Mantle, Targe, Axe Belt) Subjob: White Mage - Healer's (Earring, Mantle, Shield, Mace Belt)
There are other Latent effect items that trigger at different things such as Low HP, <100% tp, a bard song on you, This is NOT one of those items.
The only thing that activates these items is your subjob.