Terraria (Wiki): Firecracker

The Firecracker is a whip that pierces and damages multiple enemies, inflicting the Hellfire debuff (100%) for 4s. The last enemy hit by the Firecracker is targeted by summoned sentries and minions, amplified with +2.75xATK and a small explosion. The explosion is AoE, effectively applying +1.75xATK. The explosion effect is triggered again if an enemy is hit by the Firecracker. A 33% damage reduction penalty is also applied to consecutive hits.

During combat, the Firecracker sacrifices damage bonuses from debuffs for its unique explosion effect, extra hit damage, and extra minion attack damage and speed. The whip also specializes against waves of enemies albeit the noticeable damage reduction penalty, but fixable by inheriting attack speed bonuses. 

The Firecracker may also be partnered with summoning staffs such as Abigail’s Flower, Desert Tiger Staff, and Stardust Dragon Staff for increased based minion damage. As for other whips, the Firecracker’s unique summon tag effects and Durendal’s or Snapthorn’s quick swinging speed can be a lethal combination against waves of enemies.

When exploring caves or finding ores, the Firecracker produces light, aiding the player.

Despite the 33% damage reduction penalty, the Firecracker’s unique summon tag effects make it fairly good against waves of enemies.

The Firecracker is best modified with Legendary to improve all stats.