Mario Kart DS/Items

When a player runs over one of several Item Boxes found on each track, a short roulette begins, eventually stopping on an item which the player may use to his or her advantage. Which item is received is largely dependent on the player's current position in the race, and to a lesser extent the kart's item rating. Players near the front of the race tend to get items such as the Banana and Green Shell, while those near the back of the race are more likely to receive powerful items, such as the Bullet Bill and Thunderbolt.

Item List

Bananas: Banana peels are dropped behind karts and essentially function as roadblocks of sorts; karts that slip on peels are spun out briefly. They are usually dropped behind the kart, but can be thrown forward by holding forward direction key while dropping. They can also be dangled behind the kart as a shield.
Triple Banana: The same as bananas, except there are three. When activated, three bananas will appear in a row being dragged behind the kart, and can be placed on the track individually. They also function as a shield.
Green Shell: Green shells fly in a straight path and ricochet off walls up to five times until they break, fall off the course, or hit a kart. Getting hit by a green shell will cause a kart to flip over. Green shells can be fired forward or backwards, and dangled behind the kart as a shield.
Triple Green Shell: The same as green shells, except there are three. When activated, the three shells will rotate around the kart. From there they can be launched one at a time; they also function as a shield.
Red Shell: Red shells home in on the kart directly in front of the kart that uses it. To do this, they follow the track until the target is seen. Red Shells have a roundabout way of doing things, so they may hit racers from the side. They have the same effect on karts as green shells. Red shells can be fired forward or backward, and dangled behind the kart as a shield. However, red shells do not home in on a kart when thrown backward.
Triple Red Shell: The same as red shells, except there are three. When activated, the three shells will rotate around the kart. From there they can be launched one at a time; they also function as a shield.
Fake Item Box: Similar to banana peels; look like regular item boxes, but have no spinning question mark inside them. They cannot be used to block incoming shells, although, like shells, they can be held behind drivers. When using the close-up map view on the bottom screen, these boxes show up red.
Mushroom: Mushrooms give their users a short speed boost. Karts that boost into an opponent will cause them to spin out.
Triple Mushroom: A set of three mushrooms, which work the same as their single counterparts. If more than one mushroom is used at the same time, they do not make the kart travel at a greater speed than using one mushroom alone.
Bob-omb: A bomb that is thrown in front of its user and then explodes. Its effect is similar to that of the Spiny Shells. Bob-ombs are thrown forward by default, but can be dropped behind the kart as well. They can be dangled behind the kart as a shield, and this is a good idea because an explosion while dangling will not hurt the user, unless the user is next to the opponent.
Blooper: A squid that squirts ink on the top screen of every racer in front of its user, obscuring their view for several seconds. The player can still effectively steer by using the close-up map view on the bottom screen. This item causes computer-controlled players to move erratically as if they were unable to see the track in front of them. Mushroom boosts get rid of the ink.
Spiny Shell: A spiked, winged, blue Koopa shell that targets the player currently in first place, even if that player is the one launching the shell. The shell is almost unavoidable, and causes a large explosion that flips over its target and anyone caught in its blast radius. Spiny Shells will not change targets once it gets close, even if the targeted player is no longer in first place. If racers have already finished the race before the shell is launched, the Spiny goes for the closet person to finish next. The only way to avoid the Spiny Shell is to either get hit by another item that causes players to tumble over, thus negating the shell's explosion, to use a Star or Boo, or to transfer it to another person by driving right next to them as the shell homes in on the player.
Boo: A ghost that renders its user invisible (they cannot be affected by enemy attacks or terrain, or seen by other racers) and steals an item from another racer. If there are no opponents with items around, Boo will come back empty-handed.
Golden Mushroom: Gives the player an infinite amount of boosts for 7-10 seconds (depending on the kart's item stat).
Star: Gives its user a speed boost, invincibility, traction on any surface and the ability to knock down any racer they touch. Stars last for about eight seconds.
Bullet Bill: It turns its user into a Bullet Bill on autopilot, moving at high speed and smashing through anything in its way. The Bullet Bill transforms back into the kart after about 4-8 seconds (depending on the kart's item stat). This is based off of the Chain Chomp of Mario Kart: Double Dash!!
Thunderbolt: Targets everyone except the player who used the item. Racers hit by the thunderbolt lose any items they are carrying, spin out, are shrunk (making them easier to be knocked around), and slowed down. The thunderbolt can only be avoided if the player is off the course, or using a Star, Bullet Bill, or Boo when it is activated. Racers grow large again in reverse order of their positions when the thunderbolt was used.

Items during online play

In Nintendo WiFi Connection matches, the "Triple" items are disabled (except for Triple Mushrooms), and players cannot drag items behind their kart by holding the L button. This is most likely done to reduce the amount of sprites that game has to load, as the disabled items all appear around the racer with the item.