Here is a pretty much complete list of all the items in the game. Please E-mail me if you find something wrong with the list.
 

Potion-Restore HP by 100

Hi-Potion-Restore HP by 500

X-Potion-Fully restore HP

Ether-Restore MP by 100

Turbo Ether-Fully restore MP

Elixir-Fully restore HP/MP

Megalixir-Fully restore all members' HP/MP

Phoenix Down-Restore life

Tent-Fully restore all members' HP/MP, Use only at save point

Luck Source-Raise Luck

Speed Source-Raise Dexterity

Mind Source-Raise Spirit

Magic Source-Raise Magic

Guard Source-Raises Vitality

Power Source-Raises Strength

Grenade-Explosive damage on one opponent

Shrapnel-Explosive damage on all opponents

Right Arm-Explosive damage on all opponents

Dream Powder-Uses Sleepel on all opponents

Mute Mask-Uses Silence on all opponents

War Gong-Uses Berserk on all opponents

Loco Weed-Uses Confu on all opponents

Fire Fang-Uses Fire2 on all opponents

Fire Veil-Uses Fire3 on all opponents

Antarctic Wind-Uses Ice2 on all opponents

Ice Crystal-Uses Ice3 on all opponents

Bolt Plume-Uses Bolt2 on all opponents

Swift Bolt-Uses Bolt3 on all opponents

Earth Drum-Uses Quake2 on all opponents

Earth Hammer-Uses Quake 3 on all opponets

Deadly Waste-Uses Bio2 on all opponents

Kiss of Death-Casts Death on all opponets

M-Tentacles-Uses Bio3 on all opponents

Stardust-Uses Comet2 on all opponents

Holy Touch-Uses DeSpell on one ally

Ink-Uses Darkness on all opponents

Basilisk Claw-Petrifies on opponent

Hourglass-Casts Stop on all opponents

Vampire Fang-Sucks HP out of one opponent

Ghost Hand-Sucks MP out of one opponent

Dragon Scales-Water damage on all opponents

Impaler-Changes one opponent into a frog

Shrivel-Uses Mini on one opponent

Molotov-Fire damage on one opponent

S-mine-Explosive damage on one opponent

8-Inch Cannon-Explosive damage on one opponent

Graviball-Uses Demi on one opponent

T/S Bomb-Uses Demi2 on one opponent

Dazers-Paralyzes one opponent

Dragon Fang-Lightning damage on all opponents

Spider Web-Slows all opponents

Bird Wing-Uses Whirlwind on all opponents

Lunar Curtain-Casts MBarrier on all allies

Light Barrier-Casts Barrier on all allies

Hyper-Cures Sadness

Tranquilizer-Cures Fury

Vaccine-Protects against transformations

Eye Drop-Cures Darkness

Hero Drink-Raises ability once during battle

Speed Drink-Casts Haste on one ally

Smoke Bomb-Can escape from opponents during battle

Remedy-Cures abnormal status

Echo Screen-Cures Silence

Cornucopia-Cures Small

Maiden's Kiss-Cures Frog

Soft-Cures Petrify

Antidote-Cures Poison

Claudron-Casts Bad Breath E-skill on one opponent

Sylkis Greens-When you want a chocobo...

Reagan Greens-When you want a chocobo...

Mimett Greens-When you want a chocobo...

Curiel Greens-When you want a chocobo...

Pahsana Greens-When you want a chocobo...

Krakka Greens-When you want a chocobo...

Gyshal Greens-When you want a chocobo...

Tantal Greens-When you want a chocobo...

Zeio Nut-For breeding chocobos

Carob Nut-For breeding chocobos

Porov Nut-For breeding chocobos

Pram Nut-For breeding chocobos

Lasan Nut-For breeding chocobos

Saraha Nut-For breeding chocobos

Luchile Nut-For breeding chocobos

Pepio Nut-For breeding chocobos

Tissue-This one's a little tough...

1/35 Soldier-Shinra armored "attack" soldiers: 12 in the set

Save Crystal-Use in Final Dungeon

Super Sweeper-A new machine to protect the reactor
 

Key Items

Pharmacy Coupons-Wall Market

Cotton Dress-Wall Market

Satin Dress-Wall Market

Silk Dress-Wall Market

Wig-Wall Market

Blonde Wig-Wall Market

Dyed Wig-Wall Market

Disinfectant-Wall Market

Deodorant-Wall Market

Digestive-Wall Market

Cologne-Wall Market

Flower Cologne-Wall Market

Sexy Cologne-Wall Market

Glass Tiara-Wall Market

Ruby Tiara-Wall Market

Diamond Tiara-Wall Market

Member's Card-Wall Market

Keycard 60-Shinra Tower Level 59

Keycard 62-Shinra Tower Level 61

Keycard 65-Shinra Tower Level 62

Midgar Parts-Shinra Tower Level 65

Keycard 66-Shinra Tower Level 65

Keycard 68--Shinra Tower Level 66

PHS-Kalm

Basement Key-Shinra Mansion

Keystone-Dio's Showroon in Gold Saucer

Black Materia-Temple of the Ancients

Glacier Map-Icicle Inn

Snowboard-Icicle Inn

Mythril-Sleeping man near Junon

Leviathan Scales-Underwater Reactor

Huge Materia-North Corel(after stopping Coal Train)

Huge Materia-Fort Condor

Huge Materia-Shinra Rocket

Huge Materia-Downed Submarine

Key to the Ancients-Beneath Northern Continent(near Bone Village)