Lightning

Thunderbolts are attack items found in the Mario Kart and Paper Mario series. These special items summon lightning from the sky, causing various effects. Thunder has often been thought to be Luigi's counterpart to Mario's fire, but Luigi has also been seen to fire green flames, discrediting these theories.

Mario Kart
In the Mario Kart series, Thunderbolts are extremely powerful items that racers usually receive when they are in (or near) last position in a race. When used, a Thunderbolt will temporarily shrink all the other racers, making them slower and weaker.

In Mario Kart: Double Dash!! it will not affect you if you are currently indisposed. (such as having just been hit by another item, or fell over a cliff).

In Mario Kart DS, the effect of being hit by a Thunderbolt wears of quicker the lower in the rank you are. For example, someone hit by one while in 7th place will return to normal almost immediately, while those in 1st or 2nd place will remain shrunk for up to six seconds.

Paper Mario series
In the Paper Mario series, the attack item is known as a Thunder Bolt. This item summons a bolt of lightning that inflicts five damage to one enemy.

Also in the series is the much more powerful Thunder Rage. This item summons a lighting storm that inflicts five damage to all enemies.

In Paper Mario: The Thousand-Year Door, the Thunder Rage can also be cooked by mixing a Shooting Star and a Point Swap (though not the best deal).

Mario Hoops 3-on-3
In Mario Hoops, the Thunderbolt played much the same purpose, stunning all players and making the ball drop out of one's grasp.