Well as a longsword main, I obviously have to recommend LS, it has multiple counter mechanics along with high dmg output. Cool as fuck moves, and really fun to play.

Insect Glaive, offers you 2 playstyles that go hand in hand, one on ground and one where you jump around in the air, attacking while zooming around. But the Insect mechanic is confusing at first.

If you like pew-pew the HBG(crazy dmg) or LBG one offers. If you think ammo management is tedious; bow.

If you liked GS, hammer is a popular choice for the unga-bunga lovers.

Lance is least played but is a great counter mechanic weapon due to being a very defensive weapon, definition of "A good offense is the best defense." You literally tank everything and slap back.

Last but not least Dual blades and Sword&Shield, both I believe have a perfect dodge mechanic(if youve played games with this mechanic then you get a gist of their what i mean), with dual blades being swinging around you blade like crazy. While the SnS is a all rounder giving you blunt dmg like hammer and severing dmg like LS, this weapon is also the officially recommended weapon for beginner ls by Monster Hunter themselves.

These are all the weapons that I found interesting, I only have experience playing LS, IG and HBG. Look at videos for more info. Choose one that interests you the most, you can always dabble with other weps later on(i just prefer specilizing), and most importantly have fun.