So you have a Cool Sword, An Axe to Grind, or another bladed or Energy Weapon that is absurdly sharp. Sweet! Now nothing can stand in your way, not even Ray Enforced adamantium-mithril alloy bulkheads! ... except for another, equally sharp weapon made of the same material, magical enchantment, technology or by the same Ultimate Blacksmith. Why? Well, maybe your Laser Blade's containment field is naturally blocked by your opponent's. Maybe they're both so impossibly sharp that the prospect of one cutting the other is like trying to make water wetter by splashing it with more water? Perhaps since both were Forged by the Gods, their nature as Empathic Weapons recognizes a sibling and refuses to harm it?