Old Items:
Red Shell
Green Shell
Mushrooms
Banana Peels
Bullet Bill
Lightning Strike
Bob-omb
Blooper
Star
New Items:

Fire Flower - After acquiring the Fire Flower, players can throw fireballs ahead or behind their kart to trip up players.
Spiked Blue Shell - The blue shell is missing its wings this time around, so it may work a little different than its predecessors.
Tanooki Leaf - Nothing is known about this item at the moment, but it is definitely included as a nod to Super Mario 3D Land. Speculation says it may work like the feather in Super Mario Kart.
Mario Kart 7 "Seven" - Absolutely nothing is known about this item. I think it may hold a randomize function if a player happens to roll this logo.