Most of the items featured in the original Mario Kart game were recreated in this version and a few new items were also added. Items are gained by driving through a floating question-mark block.
Note: This symbol 
means an item can be thrown forward or backward.
Weapons
These are items that are directly used against other racers to cause them to crash or slow down.
Green Shell
These are fired in a straight line and can bounce off walls. They can be fired either forwards or backwards or they can be held behind a the kart to defend from other projectiles. They cause an opponent to tumble when hit. They cannot be fired across gaps, lava or deep water. If a green shell hits a banana skin, a red shell or another green shell it will 'die'.
Triple Green Shell
- New to Mario Kart 64
A bunch of three green shells which, once activated, circle the player's kart to act as a barrier against other weapons. The player can then fire these shells as normal or choose just to use them as a defensive barrier.
Red Shell
Simply put, this is a 'homing-missile' version of the green shell. When fired it homes in on the racer in front of the player. It is vulnerable to all the same things as a green shell with the additional weakness that it cannot bounce of walls - if it hits a wall it will die.
Blue Shell (a.k.a. Spiney Shell)
- New to Mario Kart 64
The most powerful of all the shell items. When fired, the blue shell chases after the racer in first place. It follows the centre of the track, crashing through anyone that gets in its way, until it finally crashes into the race leader. It causes the same type of crash as other shell types. The blue shell is invulnerable to any kind of defence or weapon, even the invincibility star.
Lightning
Possibly the most destructive item in the game but it is only available to racers who are quite far behind the race leader. The lightning bolt causes all other racers to become tiny - and much slower - for a few seconds. This is very handy for catching up with other racers. Tiny racers can also be 'squashed' by normal sized racers, causing them to spin out. Racers who are invincible when the lightning is fired are not affected.
Traps
These are items that are primarily dropped on the track in order to make a competitor crash into them.
Banana Skin
Sits on the track and causes any kart that drives over it to skid. They can either be dropped behind the kart or fired forwards. Banana Skins can also be held behind the kart to provide defence from shells.
Banana Bunch
- New to Mario Kart 64
A bunch of five banana skins which trail behind the kart. They can be dropped or fired in the normal way, or they can just be left trailing behind the kart to provide defence from shells. These trailing skins will also cause other racers to skid if they drive into them.
Fake Item Box
- New to Mario Kart 64
Similar to banana skins, in that they can be dropped, fired or held behind the kart. They look identical to a normal item box except the question mark logo is upside down. When a racer hits one of these they crash and come to a complete stop. Most dangerous when dropped in amongst the normal item boxes.
Power-ups
These are items that affect the user in some way - increasing their speed for example.
Star
Causes the user to become invincible in classic Mario Bros. style (i.e. flashing and playing the invincibility music) for a few seconds. It also causes the players kart to be faster and handle slightly better. The only thing that can harm an invincible kart is a Blue Shell. While invincible a player can also drive through hazards like Thwomps and pipes and will cause any racer that touches them to crash.
Boo
Sends a Boo (ghost) to steal an item from a nearby racer and bring it back to you. These can be used tactically in multiplayer games.
Mushroom
Gives the user a brief boost of speed.
Triple Mushroom
A bunch of three mushrooms allowing the user three separate speed boosts.
Golden Mushroom
Gives the user unlimited speed boosts for a set period of time.