Knight's Honor Achievement - Dark Souls

To get this achievement/trophy, you must complete the game 2.5 times for all the unique souls needed to craft some of the special weapons (you need 3 Souls of Sif).

Crafted Rare Weapons

To create these weapons, you must take the normal +10 weapon/shield and the corresponding unique soul to the Giant Blacksmith in Anor Londo.

To ascend a weapon to +10, you need 9 Titanite Shards and 10 Large Titanite Chunks

+1 - 1x Titanite Shard
+2 - 1x Titanite Shard
+3 - 2x Titanite Shard
+4 - 2x Titanite Shard
+5 - 3x Titanite Shard

+6 - Talk to the blacksmith outside Sen's Fortress - 1x Large Titanite Shard

+7 - 2x Large Titanite Shard
+8 - 2x Large Titanite Shard
+9 - 2x Large Titanite Shard
+10 - 3x Large Titanite Shard

You can buy Titanite Shards and Large Titanite Shards from the merchant at the top of Sen's Fortress

• Moonlight Butterfly Horn - Spear/Rapier +10 & the Moonlight Butterfly Soul
• Crystal Ring Shield - Shield +10 & the Moonlight Butterfly Soul
• Cursed Greatsword of Artorias - Broken Straight Sword/Straight Sword Hilt +10 & Sif's Soul
• Greatsword of Artorias - Dagger/Straight Sword/Greatsword +10 & Sif's Soul
• Greatshield of Artorias - Shield +10 & Sif's Soul
• Quelaag's Furysword - Curved Sword +10 & Quelaag's Soul
• Chaos Blade - Katana +10 & Quelaag's Soul
• Dragon Bone Fist - Fist +10 & Iron Golem's Core
• Golem Axe - Axe +10 & Iron Golem's Core
• Smough's Hammer - Hammer +10 & Smough's Soul
• Dragonslayer Spear - Spear/Rapier +10 & Ornsteain's Soul
• Darkmoon Bow - Bow +10 & Gwyndolin's Soul
• Tin Darkmoon Catalyst - Catalyst +10 & Gwyndolin's Soul
• Lifehunt Scythe - Halberd/Scythe/Whip + Priscilla's Soul
• Great Lord Greatsword - Dagger/Straight Sword/Greatsword +10 & Gwyn, Lord of Cinder's Soul

Found Rare Weapons

• Astoria's Straight Sword: - In the Valley of Drakes, by the Zombie Dragon
• Black Knight Greataxe - Dropped by Axe Black Knights.
• Black knight Greatsword - Dropped by Sword Black Knights
• Black Knight Halberd - Dropped by Spear Black Knights
• Black Knight Shield - Dropped by any Black Knight type
• Black knight Sword - Dropped by any Sword Black Knight
• Blood Shield - In the Painted World of Ariamis, on the bridge after the Dragon Zombie
• Channeler's Trident - Dropped by Mage in the Duke's Archives
• Crest Shield - When you revisit the Undead Asylum, kill the soldier who gave you the flask the first time you were here.
• Crescent Axe - Dropped by Patches in the Tomb of the Giants, or bought from Patches at Firelink Shrine.
• Dark Hand - Joining gift for Darkwraith Covenant.
• Demon's Spear - Anor Londo, Batwing Demon drop.
• Dragon Crest Shield - Valley of Drakes, by the Zombie Dragon
• Dragon Tooth - Anor Londo,  found in a treasure chest on the bottom floor behind a false wall
• Dragonslayer Greatbow - Anor Londo. When you get to the Giant Blacksmith, you will go up some straight stairs. To the right, you will find some big windows with one broken. Go out this findow heading right, and you will see a corpse with the bow.
• Effigy Shield - Tomb of Giants
• Giant's Halberd - Bought for 5000 souls at Giant Blacksmith
• Grant - Dropped by NPC invader "Divine Knight Leeroy" He will invade you in The Tomb of Giants.
• Gravelord Sword - Reward for joing Gravelord Nito's covenant.
• Havel's Greatshield - Anor Londo. Found in a treasure chest on the bottom floor behind a false wall
• Sanctus - Also dropped by invader "Divine Knight Leeroy" in The Tomb of Giants
• Silver Knight Shield - Anor Londo. Dropped by any silver knight
• Silver Knight Spear - Anor Londo. Dropped by Spear-type Silver knights
• Silver Knight Straight Sword - Anor Londo. Dropped by Silver knights
• Stone Greatshield & Greatsword - Darkroot Garden. Both are Dropped by any Stone Knight laying around before the Moonilight Butterfly boss. 

Boss Tails to Cut Off

• Drake Sword - Shoot off the tail of the Red Dragon in the Undead Burg
• Dragon Greatsword - Cut the tail off the Ancient Dragon in Ash Lake
• Dragonking Greataxe - Gaping Dragon
• Moonlight Greatsword - Seath The Scaleless
• Priscilla's Dagger - Crossbreed Priscilla in Painted World of Ariamis

Credits

Thanks to Kheten on reddit and the Dark Souls wiki for helping compile all this info.