Soul-Cutting Blade

Exactly What It Says On the Tin. It's a blade so sharp or evil or both that it can harm the soul itself. Some particularly sinister weapons actually consume souls. It's usually noted as a One Hit Kill weapon. It's often an Infinity Plus One Sword as well.

Most incarnations of The Grim Reaper or a run-of-the-mill Psychopomp use their scythe to separate the soul from the body, or something along those lines.

Anime and Manga

 * The Totsuka no Tsurugi wielded by Itachi's Susanoo from Naruto. It can put the enemy impaled by it into a Lotus Eater Machine for eternity, as found out the hard way.
 * The Death God itself wields a knife capable of harming souls, as it cutting off the arms of Orochimaru's soul during the Shiki Fuijin sealing technique managed to paralyze them.
 * The Lance of Longinus (a spear used to stab Christ during the crucifixion) is sometimes given this lore; it's why, in Neon Genesis Evangelion, the Lance is able to pierce an AT Field, since it turns out the AT Field is in fact the barrier of one's own soul.
 * This is essentially what the phantoms do in Final Fantasy the Spirits Within. One swipe, and your soul is instantly ripped out of your body, which falls dead on the spot.
 * Bleach: Zanpakuto directly translates to "Soul Cutting Sword".
 * Seeleschneider means much the same, although as Uryu reveals, it's not actually a sword per se...
 * Durarara has Saika, a sword that possesses its wielder and can cut souls.
 * Soul Eater has Masumune, who also possesses his wielder and consumes its soul. The Demon Weapons in general are this, at least for the soul-damaging part.
 * One issue of Eat-Man has Bolt consume and produce the blade of a sword created by a blacksmith who didn't create swords to harm people's bodies, but to cut their souls. He slashes at the bad guy of the week--it doesn't harm the guy physically, but he collapses with a stupefied look on his face, as if he was just delivered an Armor Piercing Slap (or Armor Piercing Question).

Comic Books

 * Katana from The Outsiders has a katana that not only removes the soul from the body of its victim, but traps the soul in the blade.
 * The Omicronian knife suit from DC One Million uses nanobots to constantly hone the blades so it's "spiritually sharp."

Film

 * Hercules includes an apparent reference to this in the scissors with which The Fates cut the "thread of life," a cord they cut to send the soul of a mortal being to the underworld.
 * The Grim Reaper's scythe in The Frighteners could qualify, as it will kill a human without damaging their body (generally by causing a heart attack) and can even kill ghosts/spirits (or at least.

Literature

 * The Bible is described as one of these in the book of Hebrews. "For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart." An unusual example in that unless you spend an inordinately long time sharpening your bible, it only cuts the soul, with no damage to the body or health.
 * Shardblades from The Stormlight Archive don't cut the flesh of living beings, they just pass straight through without damaging the living flesh, if the blade passes through the target's spinal cord they are dead, instantly, the soul severed, if it passes through a limb, that limb "dies", becoming numb and useless.
 * Morganti weapons from Dragaera eat souls, they are thus popular with assassins in a world where death is relatively cheap being the surest way of preventing the target from being brought back to life.
 * While the Morganti blades work as described, you wouldn't say they're "popular". They creep people out psychically if merely unsheathed; The Empire reserves its nastiest punishments for those who use them; if you want someone assassinated with one, expect to pay at least 10x the going rate and for No Questions Asked not to apply.
 * His Dark Materials has an example of this. It's made complicated by the fact that souls were 'personified' in animal form.
 * Laurell K. Hamilton's Nightseer features a cursed elven sword named Ache Silvestri which can consume souls and pass on their qualities to its wielder. It's also a Talking Weapon and Clingy MacGuffin which latches on to the heroine, Keleios, because she is half-elven and demon-tainted and therefore a perfect match for it.
 * Maybe a bit of a stretch, but Merry's sword in The Lord of the Rings is actually a special blade from Westernesse, one of the few that can actually kill the dastardly Witch-King.
 * There was also the Morgul-knife, which the Witch King uses to try to corrupt Frodo and turn him into a wraith.
 * Angels in Kelley Armstrong's The Otherworld use their Sword of Judgment to send souls of bad guys off to where they need to go. The Swords can only be used on evil people though.
 * Shows up briefly in Patricia Briggs' Masques. is injured by a soul-eating blade. In a possibly related event, it later turns out that her own sword eats magic, although somehow she never knew this.
 * In The Elric Saga, Elric's Stormbringer not only fits, but it might well be the Ur Example.

Tabletop Games

 * Force Weapons in Warhammer 40000 are weapons that channel the user's psychic power through them, allowing them to sever the victim's soul from their body. Eldar Direswords and Daemon's Soul Devourer ability have the same effect, although the rules are a bit different (the Force Weapon requires the user to take a psychic test to attempt to use the ability, while Diresword and Soul Devourer require the victim to take a leadership test to resist having their soul severed).
 * Daemon Swords from the same universe. Weapons in the form of blades that act as prisons for the essences of raging daemons, as well as being powerful artifacts of Chaos. They don't really cut your soul, so much as they devour them.
 * Dungeons and Dragons:
 * The Nine Lives Stealer sword can drain the life force/soul from the creature hit.
 * Module S2 White Plume Mountain. The sword Blackrazor's purpose is to suck out and devour the souls of its victims.
 * The Book of Vile Darkness introduced the concept of vile damage, which represents such an evil violation of body and soul it can only be cured by healing magic on consecrated ground. Naturally the same book offered up a number of ways to turn your blade into a Soul Cutting Blade--not to mention Soul-Piercing Arrows, Soul-Crushing Clubs, Soul-Cutting Spells, and so on.
 * Villains and Vigilantes adventure Devil's Domain. One evil spirit has a "Soul Sickle" that can suck out the target's soul and store it in the sickle.
 * Eberron has a type of blade enchantment called the Keeper's Fang; they don't actually have any special damage type sometimes associated with soul-cutting weapons, but they DEFINITELY qualify as soul eaters. Such blades send the soul of their victims directly to the Keeper, the setting's god of death; what happens from there is left up to the DM to decide but in no case is it a good thing.

Video Games

 * The Soul Edge from Soul Series might as well be the Trope Codifier in Video Games.
 * In The Elder Scrolls, series there is a Soul Trap spell which can be applied to any weapon (if an enemy is killed while its effect is active then their soul is bound to a "soul gem" in your inventory if there's one powerful enough to hold it). In the lore, there is a recurring sword called Umbra which possesses its owner (forcing them to take on its name) and also has this effect.
 * The Soul Reaver from the Legacy of Kain series. In its wraith blade form, it eats souls.
 * In Touhou Youmu's Roukanken is said to be able the kill ten spirits in a single stroke... though what it actually does is enlighten them, forcibly moving them to the next stage of the afterlife. On the other hand, Tenshi's Hisou no Tsurugi appears to be actually capable of killing spirits.
 * Tenshi killing spirits really pissed off usually easy-going shinigami Komachi. The one thing that prevented Tenshi from getting killed right there and then is the fact she's only the ferrywoman of the Sanzu. (Celestials only stay alive as long as they defeat the shinigami that come for them.)
 * Dragon Quest VII had a sequence that took place in a prison town, ruled by demons, where a group of trapped people were given only one possible option of escape: the only available weapon was a blade anyone could summon at any time, and would shatter the soul of anyone struck by it. Shatter ten souls, and you'd be free. Or at least, free to  The guy running the town is powerful enough to convince everyone living there that it's a bad idea (and if you do it anyway, he'll beat the life out of you). The real catch was   and continuous use of the weapon would be inevitably fatal to the user.
 * Apparently, Yunfei's sabre from Samurai Shodown. His finisher move consist in him striking his target, pull his/her soul out of his/her body and then slice said soul in half.
 * The hero of The Reconstruction uses this because of, rather than in spite of, his pacifist leanings, since damage to the body can scar or kill, but damage to the soul will always heal. (It's never explained exactly what "soul" means in this context--at first it simply seems to be the will to fight, but later events indicate that it's something tangible. In any event, he and others who damage the soul leave their targets stunned but breathing.)
 * In God of War, Hades has a pair of chain-blades similar to Kratos's that have the ability to rip the soul right out of anybody, be they mortal or immortal.

Web Comics
"Torg: "You are what you eat I guess." Turns to Chaz "You don't actually eat souls do you?"
 * In Sluggy Freelance the sword Chaz actually seems to have an easier time killing spiritual beings than physical ones; might have something to do with having a soul of its own.

Chaz: "No I surgically remove them.""