IF ONLY I COULD RENAME MY WEAPONS I WOULD TITLE THIS LITTLE GREENISH BLUE TOME "ART IN MOTION"
It has everything. Solid damage, shoots huge ricocheting typhoons with high speed, infinite piercing, homing,
and you can fire it through walls if they're just one block thick. Great for boss battles (especially ones that summon enemies or have multiple hurtboxes), fantastic for crowd control. Firing two typhoons per cast renders that "Very slow speed" moot and makes it ridiculously light on mana consumption. Give it a chance and it
will carry you through just about anything from the moment you get it all the way to the Moon Lord. Oh, and it can't be reflected by Mimics and Selenians and the likes (as far as I know, anyway), so spam away.
Bubble Gun is a pretty close runner-up -
incredible damage with a dirt cheap mana cost. The only thing really holding it back from being the champion of single combat is poor range. My go-to weapon for Moon Lord railroad farming to kill the hands and core, with Lunar Flare (a fantastic weapon in and of itself) to deal with the third eye. I've only started using Betsy's Wrath a short while ago, but I've quickly gotten attached to its splash damage and the ability to instantly remove
forty points of defense from just about anything I point it at. If only there weren't so many event bosses immune to all debuffs...
Oh, and Optic Staff. No real reason, but the Mini Twins are adorable.