CHOMPA

This small, scrappy shield -- almost a buckler -- is made from the stretched face of some hideous swamp-dwelling creature, and was created by an insane goblin wizard, or so the story goes.

• Growls and jabbers all the time, never forming coherent words, but making stealth pretty much impossible.
• The gob leads to an extra-dimensional space but everything there is consumed; this could be annoying or useful.
• Goblins recognise CHOMPA as an important cultural artefact, and will be predisposed to be at least neutral to the wielder.

13th Age:

• +4 Hit Points.
• On a natural attack roll of 8, CHOMPA bites a mêlée opponent for 1d4 damage per level.

Quirk: You are always peckish.

B/X:

• +1 Armour Class.
• On a natural attack roll of 8, CHOMPA bites a mêlée opponent for 1d4 damage.

Fighting Fantasy:

• +1 SKILL.
• On a natural attack roll of 8, CHOMPA bites a mêlée opponent for 1 STAMINA damage.

(I am inclined to restrict the extra damage to a roll of double 4 but this seems a bit churlish in comparison to the other systems, so you may allow it on any roll of 8, although that may be too far the other way.)