The “gladius” is a short sword used by soldiers of ancient Rome through the end of the 2nd Century. It was quillonless, with a short hilt; though double-edged, it was used mostly for thrusting [F. Wilkinson, Arms and Armour, pp.34-36]. We have no examples of its use in period heraldry.
Marcus Gladius bears: Tierced per pall vert, sable, and gules, overall a gladius inverted proper.
Marcus Artorius Metellus bears as a badge: Two gladii inverted in saltire sable and overall a lion contourny argent.