Rainbow Gun

The Rainbow Gun is a weapon found in the Hallowed Chest, which can be found in the Dungeon, and may be opened with the Hallowed Key. Firing the Rainbow Gun will consume 20 Mana, and fire a rainbow-like curving beam that deals continuous damage to any enemy that walks into it at a rate of approximately 5 "ticks" per second. The "rainbow" will persist for approximately 5 seconds before dissipating; or until another rainbow is fired, which will cause the first to fade.

The projectile will travel in a straight line before succumbing to gravity and curving downwards.
 * When firing 90 degrees vertically, the beam will travel in a straight line for approximately 65 blocks before curving.
 * When firing 45 degrees diagonally, the beam will travel in a straight line for approximately 4 blocks before curving, this is only because the length of the beam segments is approximately 3 blocks long.
 * When firing 0 Degrees horizontally, the beam will travel in a straight line for approximately 35 blocks before curving.

Tips

 * This weapon is very effective against almost any mob, especially groups, and works well for boss fights such as The Destroyer.

Images
The Rainbow Gun being fired from atop a Dungeon entrance.