My favorite weapons are the Zweihander, and one of the boss soul weapons, namely
the Greatsword of Artorias cursed variant [Use a Bastard Sword+10 and the Soul of Sif to ensure you get the cursed variant when creating the weapon at the Anor Londo blacksmith]. Very few of the weapons in the game are designed to deal damage to the ghost enemies in New Londo Ruins without being Cursed or using the Transient Curse item. The only issue is the weapon's requirements: 24 STR, 18 DEX, 18 INT, 18 FAI
Warning, the self-destruct system has been activated, all personnel should evacuate immediately, 5 minutes to detonation.