Legendary Melee Weapons
The Chopper (Axe)- Dammage - 86.0: Augments- Discipline & Stoneskin : Attack Speed - Slow
Score 8 perfect rounds on a return visit to The Cruicible to win this.
The Hammerthyst (Hammer) - Dammage 78.0: Augments- Barkskin : Attack Speed - Slow
Inside the windmill, behind the Oakfield demon door. (make a marraige proposal in front of the door to open)
The Maelstrom (Longsword) - Dammage 58.0: Augments- Scourge : Attack Speed - Normal
After accumulating 2000 "loyalty points" in The Temple of Shadows, make a "worthy sacrifice" between 12:01 AM and 1:00 AM at night. (usually sacrificing your spouse or a monk from the temple of light works)
The Rising Sun (Cleaver) -Dammage 61.0: Augments- Righteous Violence : Attack Speed - Normal
Donate 10,000 or more gold to the Temple of Light betwen 12:01 and 12:59 daytime.
The Wreckager (Cutlass) - Dammage 65.0: Augments- Fear Itself, Golden Touch, Barkskin : Attack Speed - Normal
Limited Edition buyers only. Found in a chest at the end of the dungeoun "Halls of the Dead". (The dive spot to the dungoen is off the Bloodstone Pier).
The Calavera (Mace) -Dammage 67.0: Augments- Flame : Attack Speed - Slow
Inside the Westcliff Demon Door, a bit BEFORE the Howling Halls.
(Must be at least 75% "Corrupt" to open the door)
The Daichi (Katana) - Dammage 96.0: Augments- Bewitching, Killerwatt, Devestation : Attack Speed - Fast
To get The Daichi Katana, go to Brightwood Tower. On top of the tower, near the Cullis Gate, there is a broken section of stone railing. Until you visit Bloodstone for the first time, there is a stone statue in the way of the broken railing. Once you have Bloodstone on your map, return to the Wizards Tower and you can "vault" off this broken section into a well Below. Continue through "Archon's Knot" as normal, and when you reach the end of the dungeoun, EXIT it. A few feet to the right after the exit is a green chest with the Katana inside.
Legendary Ranged Weapons
The Enforcer (Blunderbuss) - Dammage 177.0: Augments- Barkskin & Lucky Charm
After finishing the "Blind Date" quest, Purchase Giles farm. Find the Key to the cellar in the houses 2nd story (or on his grave if you kill him).. Go to the cellar inside the Barn (next to the ladder) and continue through the dungeoun filled with Hollow Men. The Enforcer is buried in the final sandy area of the dungeoun, your dog must have at least 4 stars in Treasure hunting (possibly 3?) to find it.
NOTE: Getting The Enforcer seems to be buggy for some.. Be sure to get this before finishing the main quest, there appears to be a glitch where you sometimes cannot aquire it after finishing the main quest in full. Also, some have said they have found it when they have had 4 stars in Treasure hunting. I can't confirm this myself.. Finally,If you already have 5 stars in Treasure hunting and can't get the weapon, return at a later time and you should be able to get it.
The Perforator (Turret Rifle) - Dammage 81.0: Augments- Fear Itself, Discipline, & Barkskin
Inside the Wraithmarth Demon Door. Bring 10 people to the door as an "audience" and listen to its play. (The Door is in the North EAST section of Wraithmarsh. Its easiest to gather 10 people from Bowerstone Market and fast travel to Wraithmarsh)
The Rammer (Heavy Crossbow) -Dammage 119.0: Augments- Ghoul, Flame, & Bewitching
Shoot all 50 gargoyles in the game. The chest is behind the broken wall inside the Gargoyles treasure room (Bowerstone Market area).
The Red Dragon (Clockwork Pistol) - Dammage 41.0: Augments- Devestation & Lucky Charm.
Get first place in the Westcliff Shooting Range competition (+175 points).
I hope this answers your question =)