Best Weapons in .hack//Mutation

You'll be able to pick up most of these early on at Lambda Entwined Ghostly Deadlands.  You can pick up the rest at Theta Bitter Fantasy Mirror World, after completing the game.

When Data Draining (shortened to DD) you are more likely to get virus cores when blue and rare items/weapons when your status is riskier.

Twin Blade
Kite, Natsume, Moonstone

• Crimson Raid (only one available) - DD Anglomore.  Found at Theta Bitter Fantasy Mirror World (bonus dungeon; complete game first).
• Fishkin - DD Squidbod.  Found at Lambda Entwined Ghostly Deadlands or Lambda Lonely Ghostly Feeling.

Heavy Blade
BlackRose, Sanjuro

• Laevateinn - DD House Golem.  Found at Theta Bitter Fantasy Mirror World (bonus dungeon; complete game first).
• Blade3000 - DD Easter Rock.  Found at Lambda Entwined Ghostly Deadlands.

Heavy Axeman
Piros

• Key Guardian - DD Easter Rock.  Found at Lambda Entwined Ghostly Deadlands.
• Key Axe - trade Ice Bar to Panta.  You'll find the Ice Bar in Delta Hideous Organ Market Scaffold.

Wavemaster
Elk, Mistral

• Wand of Pattern - DD Wander Demon.  Found at Lambda Entwined Ghostly Deadlands or at Theta Bitter Fantasy Mirror World (bonus dungeon; complete game first).
• Great Elite - DD Harpy Queen.  Found at Lambda Entwined Ghostly Deadlands or Lambda Lonely Ghostly Feeling.

Long Arm
Gardenia, Nuke Usagimaru

• Jishawen - DD Harpy Queen.  Found at Lambda Entwined Ghostly Deadlands.
• Super Wufei - trade Chinese food to Annri.  Chinese Food can be found at Lambda Capricious Unending Corridor.

Blademaster
Mia, Rachel, Marlo.

• SWORD - DD Mad Witch.  Found at Lambda Entwined Ghostly Deadlands.
• Bureido - DD  King Worm.  Found at Theta Bitter Fantasy Mirror World (bonus dungeon; complete game first).