Mario Kart Wii/Items

By driving through an, you'll get an item that will help you - or hinder your rivals - during the race. Some items are more useful than others, and the further up the field you are the less powerful items you'll receive. Star, Mega Mushroom and Bullet Bill are example of the most powerful items in the game as they provide speed boosts and invincibility.

Mushrooms
Mushrooms give you a speed boost, except for the Mega Mushroom, which also allows you to squish enemies. when using mushrooms, your kart is not slowed down by off-road conditions.

Mushroom
A single-use mushroom to give your racer a temporary speed boost. Great if you need to cross an offroad area.

Triple Mushroom
Three mushrooms together, to give you three separate boosts.

Golden Mushroom
Gives you a potentially infinite number of speed boosts, but only stays in your item slot for a short time after the initial use.

Mega Mushroom
Makes you much bigger which allows you to squash other players on contact, making them slow down and lose their items and give you a little speed boost. You are invincible to almost everything except Star, Bullet Bill and Blooper and you're immune to off-road slow down effect. If the Lightning is used, you return to normal size.

Shells
Shells are offensive weapons, fired at other racers or just dropped behind you as an added obstacle for your rivals.

Green Shell
Travels in a straight line after being fired, and bounces off walls for a short while before it breaks.

Triple Green Shells
Three Green Shells. Pressing once will cause the shells to start orbiting your racer, forming a protective shield around the vehicle against other racers and most items.

Red Shell
Travels along the track, homing in on the person in front of you. Can be blocked using an item held behind your, or avoided on some tight corners. it does not bounce off walls and will break instead.

Triple Red Shells
Three Red Shells. Pressing once will cause the shells to start orbiting your racer, forming a protective shield around the vehicle against other racers and most items. They will follow the player closest to you and hit them.

Spiny Shell
An advanced homing weapon, that flies over the track and takes out the race leader - as well as anyone else in the vicinity - with a giant blue explosion. The Spiny Shell cannot be blocked or avoided, unless the target has an activated Star, or is using a mushroom at the exact moment of impact. It's not advisable to fire this weapon if you are in first place.

Dropped Items
These items are dropped behind your vehicle as obstacles to other racers, but can also be fired ahead.

Banana
Causes anyone who runs over it to spin out of control for a few seconds, and can block Red Shells. Hold side on the to hold it behind you.

Triple Bananas
Three bananas. Pressing once will cause the Bananas to trail behind your kart, protecting you from incoming Red Shells; press the button again to use a Banana normally.

Bob-omb
Explodes, causing anyone in the vicinity to lose control for a few seconds. Usually has a delay, but explodes prematurely if an enemy comes within the blast radius. Explodes very quickly when dropped backwards. Pressing will throw it very far, whereas pressing  or  will throw normally.

Fake Item Box
From a distance, looks like a regular Item Box with an upside down question mark and a slight red tint, but will cause any racer who drives into it to lose control for a few seconds. It also does not have the ability to block/stop other items coming from behind (e.g. Red Shell).

Bullet Bill
Transforms you into a giant Bullet Bill which makes you rocket down the track at high speeds on auto-pilot. Bullet Bill is unstoppable, invincible to everything and able to knock any player aside that comes in contact with him, which makes him drop all items in his possession.

Star
Makes your racer invincible for a short period, and increases the maximum speed and acceleration of your vehicle for the duration. The Star also allows you to drive off-road without suffering any slowdown and to knock over other players, forcing them to drop their items. It's a good idea to experiment with this like trying to run an invincible person over while you are invincible and in Mega-mushroom state or getting hit by a Bullet Bill when you are invincible.

Blooper
Sprays ink across the screens of your opponents, temporarily preventing them from seeing the track clearly. Can be cleared off faster than normal by using a Mushroom boost, or a booster on the track, but not by boosting with drifts or tricks. If you are in one player mode, the computer gets spurted with ink and you are right behind them, this is a great time to over take because they are slower when this happens. However, the ink will wipe off them faster because they are behind you.

POW Block
Causes a quake that bumps all other racers off the ground, causing them to lose control temporarily. It can be avoided if your car is in the air at the moment of impact. You can also use the trick button as the third quake goes off to reduce the impact you receive. It can be also avoided when doing the wheelie at the correct timing.

Thunder Cloud
If you get a Thunder Cloud, it activates right away. The Thunder Cloud hovers above your racer temporarily increasing your speed, and after a short period fires a lightning bolt that shrinks you. Can be passed onto other racers by bumping into them.

Lightning
Fires a lightning bolt on all other racers, shrinking them and reducing their speed. If a racer is in the air, or over a jump at the time, they will fall straight down. Racers closer to first place will be shrunk for longer, whereas players close to last will be shrunk for a very short duration.