Mario Kart DS contains 17 different items, all hidden in item boxes scattered around a track. After driving through an item box a player will get an item selected by the game.
The selection process is not completely random. The item a racer will get depends on the position the racer is in. The racer is in first place will always get a defensive item, such as a banana or a green shell. Racers in a lower positions are more likely to get offensive items which help the racer take a higher position in the race.
There are two main types of item available: Weapons and Power-ups. Weapons include shells, bananas and lightning bolts, and power-ups include speed boosts and invincibility.
Some weapons can be dragged behind the kart to offer protection against weapons from behind. This is done by holding down on the D-pad the pressing and holding L. Releasing L will drop the item. When dragging an item, the racer's item slot becomes empty and can therefore be filled with another item. Dragging items is not possible in Nintendo Wi-Fi Connection mode.
Banana
The most common item in Mario Kart DS, the banana can be thrown forwards or dropped behind. When used, bananas sit on the track creating an obstacle. When a character runs into it, the banana makes them spin out and momentarily stop. Bananas can also be dragged behind the kart for protection.
Blooper
When used, Blooper's go to every opponent ahead of you and throw black ink in their faces. This makes CPU racers slow down slightly and weave all over the track. When used against a human opponent a black smear covers part of the screen seriously obscuring their vision, but there are not forced to slow down. It is possible to steer and avoid obstacles by using the lower screen when you have ink over the main screen. The ink can be wiped off by using a mushroom, or hitting a zipper.
Blue Shell
The most powerful shell in the game. When a player uses the blue shell weapon, they send a powerful flying bomb shell that seeks out whoever is in first place and then drops it on them. It also creates a small blast which will any other racers who touch it spin-out (in the same way as hitting a banana). The original target and anyone else caught in the after blast will lose any items they currently have. If you are in first place, the only ways to avoid getting hurt by the blue shell are to drop a Bob-Omb right before getting hit, using a Boo, using a Starman, or using the Blue Shell dodge technique. Obtaining Bob-Ombs, Boos, or stars is very rare when in first place.
Bob-Omb
Similar to the banana, except the Bob-Omb explodes violently. The Bob-Omb can be thrown forwards or dropped backwards and will stop wherever it lands. The Bob-Omb explodes within a few seconds of being thrown, making it a very dangerous weapon. Anyone within the blast radius is stopped and loses whatever item they have. Unlike the banana, the Bob-Omb cannot be dragged behind.
Boo
When used, Boo may randomly steal a weapon from another opponent and give the stolen weapon to the player who summoned Boo. In addition, Boo makes you invisible and invincible when used, allowing you to pass through other players, their items, and any course obstacles like Goombas.
Bullet Bill
A new addition to the Mario Kart series, Bullet Bill will hook onto the player's kart and then both boost and auto-drive the kart for a few seconds. It will also hit and stop any other players who bump into it. Use caution with Bullet Bill on tracks such as Rainbow Road where you can fall off. When he finally drops you you will be going straight and may shoot off the track if you are not prepared. You can steer him slightly with D-pad left and D-pad right. Bullet Bills are very rare unless you are in, or near, last place.
Fake Item Box
One of the most basic weapons in Mario Kart, the fake item box impersonates an item box when it is thrown. When hit, the fake item box makes the racer tumble and then stop. Three things distinguish these fakes from real item boxes: fake boxes don't spin; the question mark logo on fake boxes is upside-down; they show up as a different colour on the lower screen. This item can be dragged but rarely offers protection against shells.
Golden Mushroom
A rare version of the mushroom in which you are given an infinite number of boosts within a small length of time instead of just getting one boost. Being off-road does not affect mushrooms much, so mushrooms are very useful to use, or create short-cuts over grass, sand, chocolate powder, etc.
Green Shell
When fired, the green shell will travel in a straight path until it either disappears or hits a player, which will make them tumble and then briefly stop. It can also be fired backwards, but goes much slower this way. The green shell can bounce off walls, to a maximum of three times. This item can be dragged behind and offers very good protection against shells.
Lightning Bolt
A rare item during Mario Kart DS races, the lightning bolt hits all players (except whoever threw it) with a bolt of lightning, which shrinks the players, slows them down, and makes them drop whatever item they were carrying. Lightning can be avoided by hitting another item (such as a Bob-Omb or shell) at the exact same time the lightning strikes, or having a Boo/Starman in effect. The effect of the lighting bolt depends on your position in the race. The effect is shorter for those who are closer to 8th place and longer for those closer to 1st.
Mushroom
Provides a small boost for the player who uses it. Being off-road does not affect mushrooms much, so mushrooms can be used to make short-cuts over grass.
Red Shell
Similar to the green shell but with one major difference - the red shell will lock on to a player and then follow it. Instead of using its classic, straight approach to its target, it now uses a kind of curved approach which makes it more difficult to avoid by dropping an item to intersect it. Red shells will disappear if the hit a wall or another item such as a banana or green shell a wall. This item can also be dragged or fired backwards, but when fired backwards it loses its homing properties.
Starman
The rarest item in the game, the star provides the player with temporary invincibility as well as increased speed and handling. Also, if a player using the star comes into contact with any other racer, that racer will crash in the same way as when they are hit by a Bob-Omb or Bullet Bill. Use caution when on tracks with edges you can fall off of as the extra speed from the star makes steering feel different.
Triple Banana
Same as the banana, but instead you are given three. This item can be dragged behind but unlike other draggable items you only have to press the item button instead of holding it down for to keep dragging it. Dragging the triple banana offers excellent protection against shell from behind. Note that this item is not obtainable during a WFC match.
Triple Green Shell
Same as the green shell, but you are given three green shells instead of one. Can also be used as a shield because the shells rotate your kart until they are fired. This item is also not obtainable in WFC matches.
Triple Mushroom
Just like a mushroom, only there's three of them.
Triple Red Shell
The same as the red shell, but you are given three. Just like the triple green shell, you can also use this weapon as a shield as the shells rotate your kart until they are fired. Once again, this item is not obtainable in WFC matches.