So, if you ask around in Terraria, you'll encounter a whole host of people who each have different opinions about what the "best weapon" in Terraria is. Shadowbeam Staff, Razorpine, Flairon, Tactical Shotgun, Coin Gun. I think there is no best weapon; this is entirely dependent on the situation. I have included a list of good weapons against certain bosses here.
Eye of Cthulhu
The game's "first" boss, a giant eye, can be taken down pretty easily with low-tier weapons. I personally use the gem staves, but most weapons will suffice. Here are a few of my personal favorites.
- Gem staves: For my first ever Eye of Cthulhu fight, the Topaz Staff was my chosen weapon. Due to its low mana cost and relatively high damage, it took down this ocular menace with little trouble. Piercing the Servants doesn't hurt either.
- Stronger bow: I've defeated the Eye with a strong type of bow many times. I believe Silver or higher is the way to go.
- Spear-type weapon: Spears are basically the only method of defeating the Eye in melee. I've used the Trident and sometimes just the default Spear against the thing. It's a bit more difficult, though.
Eater of Worlds
Ah, it's that thing again. The thing you can kill by thinking about it. Game's easiest boss, in my opinion, so long as you have a piercing weapon.
- Copper Shortsword: Just kidding, though it's been done. This is the Eater of Worlds, people.
- Vilethorn: This lingering, thorny spine can deal damage to many segments at once.
- Ball o' Hurt: My chosen weapon, a powerful flail that can be left to dangle through the giant worm and destroy it.
Brain of Cthulhu
Lowest health of any boss in the game. This thing is not a piece of cake, but it's not exactly difficult. With an interesting style and a deadly Crimson arena to fight it in, you can only kill it by looking at it... thinking about a brain isn't helpful.
- Space Gun: This, or any other piercing weapon (gem staves, ho!) is handy to decimate the Creepers quickly.
- The Rotted Fork: Piercing the creepers, this long spear is perfect for keeping the Brain out of your hair in its second phase.
- Minishark: Most of my suggestions from here on out will involve the Mini or Megasharks. They're just amazing.
- Sniper Rifle: Just for curiosity. Don't actually use it. But it is possible to one-hit the Brain with this baby.
This hard-to-find boss drops valuable loot for its point in the game, if you can find it. Its powerful charging attack makes it dangerous, but it's really a pushover if you can take it down quickly.
- Minishark: Use this while it's hovering. There's really not much else to do.
- Space Gun: Fast and can pierce the minions. Not Minishark, though.
- The Meatball/Ball o' Hurt: It's handy to strike it while it's charging.
The guardian of the Dungeon is possibly the hardest pre-Hardmode boss excluding the Wall of Hamburger. It is not too difficult, but not too easy either.
- Minishark: Just be sure to hit it since it's fast.
- Gem staves/Space Gun: These things are great against it, particularly if arms get in the way.
Wall of Flesh
Hardmode's guardian boss, a difficult creature made out of flesh. Terrible intro. But anyway, while not easy, it's not that hard.
- Demon Scythe: I cannot stress this enough, it is worth it to farm those demons for this powerful piercing weapon.
- Gem staves: If all else fails. I used a Ruby Staff.
- Boomstick: This odd suggestion can rip past the Hungry and kill the boss.
Since its upgrade, it has become a lot tougher. However, it can be killed pretty easily by a piercing weapon of sorts.
- Magical Harp: If you can be bothered to fight the Twins first, this thing is great against it.
- Golden Shower: Gross. But it pierces the thing pretty well, so to heck with it.
Double trouble's epitome is no piece of cake, competing with Skeletron Prime for the hardest mechanical boss, but they can be taken down with good dodging skills and total awesomeness.
- Megashark: This insanely fast firing weapon can take down powerful bosses better than its little brother.
- Shotgun: Attack from afar, blast them all.
This nasty character, the mother of all Swiss army knives, is probably the toughest mechanical boss. With all its implements combined, it has more health than Plantera, and a lot of nasty ways to dismember you.
- Megashark: Just aim for the head!
- Rainbow Rod: Control it well, young Jedi, and get it between all those stupid appendages.
Plants... plants... and pants. I mean, plants. Plantera is widely recognized as the second-hardest boss in the game, and used to be hardest. This plant
monster creature thing is powerful and doesn't get out much - it enrages if taken out of its home.
- Megashark: Need I say more?
- True Night's Edge/True Excalibur: Pretty much the only option for melee.
- Hallowed Repeater: Y u no make Megashark?
Put it next to Plantera or even the Twins, and we have a new definition of "pushover." Good loot, though.
- Chlorophyte Partisan/Mushroom Spear: This takes advantage of the Golem's inability to pass through walls - and the spore clouds' ability.
- Vampire Knives: Yes, yes, oh god yes. Vampirism.
The Eater of Fish has awoken!
...nope. It's Duke Fishron, Drowner of Souls and Quencher of Life Itself! This guy is easy once you get over being attacked by a fish-pig.
- Shadowbeam Staff: Silver style has been confirmed to be an accident.
- Inferno Fork: This thing is quite viable, in fact. Fishbacon, very not rare!
- Razorpine: Good lord, that thing is a machine gun for trees. I hate hugging Christmas trees.
Terraria isn't all bosses. These situations have good weapons for them too.
Invasions, where many monsters come at once, are best handled with an infinite piercing weapon.
- Heat Ray: Watch them scream as their flesh shrivels. World record Destroyer speedkill, right there.
- Magical Harp: I can't play the harp. Terrible music kills.
Tight spaces are best handled with something that hits fast. Don't get hit too many times. Ricocheting stuff is good too.
- Muramasa or the like
- Terra Blade
- Shadowbeam Staff
Shooting around corners is a good way to avoid conditions such as death. Homing weapons are the best choice here. These include:
- Spectre Staff
- Guns with Chlorophyte Bullets
I hope this guide helped. Remember: There is no single best weapon in a game this complex.