One for each, or pick ones that many characters can share. Lina, Fia, Serene and Cierra can use rapiers, for example.
Here's some general guidelines of what items what characters can use. You can try to remember how each item sounds by learning as your game progresses. I'll post what I remember here too, just in case. The same item lines share the same sounds, +additional elemental damage sounds in case of some. So if you pick up two rapiers, you won't know what is what unless you activate an overskill that tells the difference,. The easiest way is to use level 3 overskill, because characters will announce the moves.
Item : sounds : characters
Einherjar: that "thrash" slash sound most of you are probably familiar : only Ein.
Lorelei : three slow combo, followed by whoosh and a single thrust : Available for Ledda only in stage 1. This item is mandatory for that stage.
Rapier : fast three hit combo, or fast three clang for Cierra : Ein (level 2), Fia (level 3), Serene, Cierra.
Bow : a slow single thwap : Ein, Fia (level 2), Lina (level 3), Cierra.
Scythe : a single thwap faster than bow, a clang for Lina : Ein, Lina (possibly level 2), Serene (level 3).
Staff, rod or wand : two thwaps for ein, healing ring for Fia, two clangs for Cierra : Ein, Fia (level 2), Cierra (level 3).
Spellbooks : a thwap followed by occassional elemental damage for Lina, healing ring for Fia, and an elemental damage sound for Cierra : Lina, Fia (level 2), Cierra (level 2).
Orbs : a single zwing sound for all, a whoosh, plunk, follows by occasional elemental damage for Lina : any characters, but mostly Ein, Serene and Lina may be able to use overskills. Different orbs are skillable by different people, unlike other items.
Clock : some tick tocks and whoosh, high for forward timing, low for backward timing : all characters. clocks usually don't have overskills, but if so, possibly only Cierra can learn it.
Special swords : A whoosh followed by several thrust and push attacks : only Fia can use these. They're available in stage 4 on, and only at special places where you need to pull them out, like Zantetsu. You'll know if one is Fia's sword if there's an option for her to remove it by herself. These don't include dragon killer lines.
Dragon killers : a whoosh followed by a thwap, a slash or something along that line (I can't remember how the last one sounds) : only Ein can use these. They don't have the option for Fia to retrieve them.
Spears/lances : two slow thwaps for Ein, two slow clangs for Fia and Serene, two faster thwaps for Lina : Ein (level 2), Fia, Lina, Serene.
Magic broom : delayed and slow healing ring for Fia, a quick tick tock and whoosh for Cierra, a whoosh and a thunk attack for Lina: available after helping Nana mop the floor in stage 5 something. Fia, Lina and Cierra can use, but only Cierra can learn overskill.
Black earrings : two powerup whooshes : any characters. No overskill.
Potions : healing ring : all characters.
Brewable herbs : silence for most, a zip and a bling for Fia : only Fia can learn the overskill and change it to potion. It'll stay in its slot after being brewed, and there's no need to rebrew it again in the next battle.
Eggs : wet cracks for most, the same zip and bling cook sounds for Cierra : Anyone can use, but they'll just waste the usage and don't really do anything useful with it. However, Lina can waste the egg by throwing it at someone's face as an overskill. Cierra can make more use of it by frying as an overskill as well.
Steaks : Fia will return a bling, after may be a comment of her not eating meat. The same cook sounds for Cierra : Anyone but Fia and Cierra can eat steaks raw. Cierra can learn a skill and turn it into a cooked steak with more healing potency which all but Fia can use.
Ribbon : a bling for everyone, a bling and a whoosh for possibly Fia or Lina, or just Lina : given by Nono when you talk to her for the first time after stage 1, anyone can use it, but it's pretty useless except for Lina who can learn a skill to tangle someone weakly with it. I usually get rid of this as soon as possible though.
Cards : a magical hum and then a clang or several clangs, depends on how much power it can draw : this is a nifty item that can draw power from enemies and transfer back to you. Anyone can use it.
Holy orb : a bling for everyone : the normal skill is useless. Only Lina and Fia can learn overskills from it. This item is the exl for Fia, meaning she can learn a level 3 execution level overskill from it. The skill is Banishment, a powerful destruction attack that kills every enemy on screen that comes in contact with the skill. Doesn't work on bosses or enemies that can't be killed though.
Claw items : three fast thwaps for Lina and Serene : this item line is quite powerful even though they don't have level 3 overskills. Lina can learn level 2 from them I think, and Serene can learn level 1. Only these two characters can use this item line.
Whips : three slow thwaps for Lina and Serene, two faster and one slower thwaps for Cierra : Lina, Serene and Cierra (level 2).
Spider webs : a whoosh, a slide and some zoom+tick tocks : anyone. This is a binding item with no over skill.
Slime balls : an egg sounding wet squishy cracks, then whoosh and tick tocks : another binding item available to anyone.
Smoke bombs : a plunk : these unskillables are to decrease enemies' chance to hit us, available for anyone.
Seneca qui : a whoosh and healing rings for fia, a whoosh and fire blast for Cierra : obtained from ripped book pages in stage 4. Only Fia and Cierra can use it.
Naga fang : a whoosh and a thrash for Lina, a whoosh and a zwap for Ein : Ein and lina can use this one. It's gotten from killing a naga in stage 1. Only Ein can learn a level 1 lightning over skill from it though. Lina can bind someone with its successful attack.
Tips for using these items : anything you do moves your character, from scrowling to executing skills. If you have savestate, using save after each successful attacks or before executing several healings is advised. If you use an item on someone and miss, reload the state to before that round, move your curcers up and down slightly in the different ways than the first time you do, for example, if you hit down once, change to hit up twice, or down up down, or down up down up down etc. If that doesn't work, try changing your position in the select menu. The position changing doesn't have to be successful. Even a failed one moves your character. Try repositioning and go for ups and downs combination, or open an overskill then close, then execute that item again til it hits.
Also, powerful mobs with full overdrive Gage can break out of your bindings, even if it's a successful hit.
There're way more than this I can't think of right now. I'll add later if I find any.
My sskype : mars.bhuntamata, add away buddy. If you think you are crazy, I am as well. I may be even crazier, who knows.