Sonic:
Light Speed Shoes: Sewer in Station Square.
Crystal Ring: Elevator on second floor of hotel.
Ancient Light: On rock near bridge to Angel Island.

Tails:
Rhythm Badge: Follow Tikal to past (it is on a pyramid)
Jet Anklet:In the sewer behind Twinkle Park.

Knuckles:
Fighting Glove: In the cave near Angel Island.
Shovel Claw: On a cliff behind Big The Cat's house. Go to the Mystic Ruins and go to the ledge where you entered the level. Turn to your right. The Shovel Claw can be found right above Big The Cat's house. They allow Knucles to do an attack similar to Sonic's Homing attack.

Amy:
Warrior Feather: Defeat Hedgehog Hammer for the first time.
Long Hammer: Defeat First Place score again.

Big The Cat:
Life Belt: In the lake in the cave leading to Angel Island.
Power Rod: In Forest under Big's bed.
Lure 1: In Sewer Behind Twinkle Park.
Lure 2: In a cave in the Forest.
Lure 3: In the Icecap level.
Lure 4: In a prison cell on the Egg Carrier.

E-102 Gamma:
Jet Booster: In the Ammunition Room of the Egg Carrier.
Gun Upgrade: In the room opposite the Ammunition Room.