(In No Order)
Heros
Extreme Gear (Sonic Free Riders/Zero Gravity) , Hoverboards, Snowboards, Skateboards, etc.
Tornado X (Sonic X)
Light Speed Dash Shoes (Gold Version from Sonic Unleashed)
Classic Sonic's homing attack
Classic Sonic's Boom Box
Sonic Underground instruments
Jet's Gravity Ring (Sonic Zero Gravity)
Omochao
Caliburn
Arondight
Whatever Skyrim stuff Dovahshy has.
Link's tunic, hat, and gloves (from Sonic Lost World's Legend of Zelda DLC)