Explosive Tag

The Exploding Tag (起爆札, Kibaku Fuda) was an item coming from the Naruto franchise in Super Smash Flash 2. According to SSF2 Developer, TSON, it was removed from the game because it was considered an "ugly" item. In January 26th, 2015, Tid, another SSF2 Developer, revealed in the Smash World Forums that it was removed because it randomly caused some game-breaking glitches a few days before releasing a build and may return in a future update.

Origin
Exploding Tags are scraps of paper inscribed with a special writing, centering around the kanji BAKU (爆, lit. "Explode"). Infused with chakra, they will explode after a set amount of time, remotely, or after being ignited by flame. The tags can be attached to a surface or wrapped around a weapon to be thrown at an enemy.

They are very versatile and of the most basic ninja tools. Ninja can confuse their enemies by obtaining fake exploding tags. They work even under heavy rain.

When an explosive tag is detonated remotely, ninja tend to use the "Snake" hand seal. Similarly, when used remotely, exploding tags can be detonated in sequence, allowing them to be used to trap opponents.

In Super Smash Flash 2
Every Exploding Tag would come attached with a kunai so they can stick on oppoenets or any other surface. Unlike the Naruto series, it didn't need to be infused with chakra as the tag ignites automatiacally after it sticked on something. Players who got hit by the tag must act fast as it could explode in any moment.

Trivia

 * Due to complications with some bugs, the Poké Balls, Assist Trophies, Bumpers, and Exploding Tags were disabled on demo v0.9b and has been added in patch 0.9.1.1965.
 * Out of the four items, the Exploding Tag was the only item that didn't return.