1) Terra Blade. After its buff this cracker can destroy just about anything in seconds, and with beetle attack armor it liquefies bosses.
2) Bubble Gun/Razorblade Typhoon/Flairon/Tsunami/Tempest Staff. I know, that's a lot, but all of the Fishron weapons are insanely fun to use, notably the Tsunami with Hallowed Arrows.
3) Shadowbeam Staff. I have a lot of fun sending this around corners and everywhere throughout enclosed spaces, and it's very useful too.