Highest damage weapon?

Coin Gun is the most powerful weapon, if platinum coins are used as ammo, which can deal 200 damage and has an insanely fast rate of fire.

If you want to see each weapon sorted for its Damage or Damage-per-second, see here.

As of 1.4, the strongest single-target weapon is the Zenith, which can deal around 70k DPS at its maximum. It averages roughly 30k DPS in standard gameplay, and can also hit multiple targets, making it the best all-around weapon in the game.

This surpasses the Coin Gun's 1735 DPS, although the Coin Gun remains the best ranged option. You may want to use the S.D.M.G if money is a concern.

The best magic weapon remains the Last Prism (although it has an ungodly mana cost), but the best summoner weapon is the Terraprisma. However, the Stardust Dragon Staff and Stardust Cell Staff still serve as viable weapons for lategame with specific builds.. The Kaleidoscope serves as the best Whip option (whips are summoner weapons also added in 1.4), though if you're using the Stardust Dragon Staff, the Firecracker may be preferable as it increases the dragon's damage more than the Kaleidoscope does.

The best melee weapon in the game is the Terrarian. While Coin Gun and Meowmere seem better, the Coin Gun requires a lot of money if you want high dps, and the Meowmere can deal mostly 1000 damage with a projectile, while the Terrarian deals 190 dmg and throws projectiles with the same damage, AND if combined with the Yoyo Bag, it's dps get's to 5000 easily, and that with a single enemy.

In conclusion, the Terrarian is the best melee weapon, the best ranged weapon is the S.D.M.G., the strongest magic weapon is the Last Prism, the strongest summoning weapon is the Stardust Dragon Staff, and the strongest sentry is the Rainbow Crystal Staff(excluding the Tavernkeep's sentries, which the best is Ballista staff).