Oh indeed, but the problem with 'legendaries' is that most of them were useless, and a few of them were overpowered. It felt like they were just trying to slap Skyrim's enchantment system onto Fallout.

I think an "ideal" legendary weapon property is one that makes the weapon conditionally useful, something where you may have to adjust how you play in order to make full use of it. Here's an old list I had laying around.

• Armored: Damage multiplier of your physical armor over your energy armor.
• Auto-loading: Ammunition steadily moves from ammo supply to magazine at a fixed rate, up to magazine capacity, but weapon cannot be manually reloaded.
• Betrayer: Deals massive damage to creatures that are friendly or neutral towards you (and for five seconds after they turn hostile), deals half normal damage to other targets
• Blood sucking: Each shot costs hit points rather than ammunition, based on the ammo type. .38 costs very little HP, fat man nearly kills you.
• Center mass: Deals bonus damage to non-VATS shots to the torso, but half damage to limbs and head. In VATS increases torso hit chances, reduces head and limb hit chance, and no bonus damage.
• Disposable: This weapon comes with a large supply of ammunition in the magazine (Such as 999 rounds for a .38 or 5mm weapon) but cannot be reloaded and is destroyed when the last bullet is fired.
• Executioner: Increases chance to hit in VATS on targets below 25% health, severely decreased chance to hit on targets above 25% health.
• Fallout: Humans and super mutants killed with this weapon may turn into frenzied feral ghouls that explode upon death.
• Focused: When a creature is hit by this weapon, that creature becomes the marked target for 1 minute or until it dies. Weapon deals bonus damage to the marked target, but negligible damage to other targets.
• Gatling: Automatic weapon fires faster the longer you hold down the trigger, but keeps firing for a moment after you release the trigger.
• Jealous: Damage multiplied by the ratio of the target’s armor to your armor for the weapon’s damage type. So if you have 100 armor and the enemy has 200 armor, it deals double damage. If you have 200 armor and the enemy has 20 armor, it deals 10% damage.
• Kinetic: Weapon deals damage bonus based on how much the user has run in the past minute, can only be fired while moving.
• Loose gears: Automatic weapon accuracy increases and recoil decreases the longer you fire, sometimes uses more than one ammunition per shot.
• Loot Pinata: Creatures killed by this weapon drop significantly more loot, but all their loot flies away from the corpse at random velocities and angles.
• Marxman: Deals bonus damage to enemies with caps in their inventory, but foes killed by this weapon will have no caps in their loot.
• Money to burn: Uses caps for ammunition, with the cost of each shot equal to normal barter price x1.5.
• Nudist: Has a chance to knock off armor pieces of humanoid targets (Similar to power armor mechanic), but only pieces with a higher armor value than what the user is wearing.
• Spray & Pray: Has a high chance not to consume ammunition on a per-shot basis when fired, but comically terrible accuracy and recoil.
• Sputtering: Fire rate varies up and down as you fire it, but overall is higher than normal.
• Wheel of misfortune: Deals +200% damage to one specific limb (Left arm, right arm, left leg, and right leg), but only 50% damage to any other body part. When you hit this part on a target, the bonus changes to a random new limb (message indicator in top-left)