If two different items are shown, the first listed is the most frequently
found on that Pokemon.
If two items that are the same are shown, there is a higher chance of it
being caught with this item than if only one item was listed, or if two unique
items were listed.

I ran 100s of trials and have determined there is a 25% chance of catching a Pokemon
with the first item shown below, but only if he can have 2 items, such as
Clefairy or Growlithe. Otherwise, if the Pokemon has only 1 item listed below, there is a
1 in 64 (1.5625%) chance of it being caught with that item...

Onto the list! 

Butterfree 
Bright powder

Beedrill 
Poison Barb

Fearow 
Sharp beak 

Pikachu 
Berry 

Raichu 
Berry

Clefairy
Mystery Berry
Moon stone

Clefable 
Mystery Berry
Moon stone

Vulpix 
Burnt Berry
Burnt Berry

Ninetales 
Burnt Berry
Burnt Berry

Paras 
Small Mushroom
Big Mushroom

Parasect 
Small Mushroom
Big Mushroom

Growlithe 
Burnt Berry
Burnt Berry

Arcanine 
Burnt Berry
Burnt Berry

Poliwhirl 
King's Rock

Poliwrath 
King's Rock

Geodude 
Everstone

Graveler 
Everstone

Golem 
Everstone

Slowpoke 
King's Rock

Slowbro 
King's Rock

Magnemite 
Metal Coat

Magneton 
Metal Coat

Farfetch'd 
Stick

Dodrio 
Sharp Beak

Grimer 
Nugget

Muk 
Nugget

Shellder 
Pearl
Large Pearl

Cloyster 
Pearl
Large Pearl

Cubone 
Thick Club

Marowak 
Thick Club

Chansey
Lucky egg

Horsea 
Dragon Scale

Seadra
Dragon Scale

Staryu 
Star Sand 
Star Scroll 

Starmie 
Star Sand 
Star Scroll 

Mr.Mime 
Mystery Berry

Jynx 
Burnt Berry
Burnt Berry

Magmar 
Burnt Berry
Burnt Berry

Snorlax 
Leftovers
Leftovers 

Dratini 
Dragon scale

Dragonair 
Dragon scale

Dragonite 
Dragon scale 

Mewtwo 
Berserk Gene

Mew
Miracleberry

Otachi 
Berry

Ootachi
Berry
Gold Berry

Pichuu 
Berry

Pichu
Mystery Berry
Moon stone

Politoed 
King's Rock

SlowKing 
King's Symbol

Misdreavus
Spell Tag

Scizor 
Metal Coat

Shuckle
Berry
Berry

Sneasel
Quick Claw

Kingdra
Dragon Scale

Smoochum
Ice Berry
Ice Berry

Magby
Burnt Berry
Burnt Berry

Miltank
Moo-Moo Milk
Moo-Moo Milk

Blissey
Lucky egg

Ho-oh
Sacred Ash
Sacred Ash