To be honest, I was shocked at the variety of daggers found in LOTRO. Just the sheer number of skins rivals that of the swords was incredible. This particular weapon class will be handled in two parts, each entry having approximately thirty daggers each. I've opted to ignore the most common appearances for the moment, like the Boot Knife and the Bronze Dagger, given that they make up for almost fifty percent of the game's daggers and how easily they're crafted, looted, or purchased from early game vendors.
As usual, if you see another way of obtaining a skin shown here, please let me know in the comments!
Aeglang - Bartered from Forgamdir at Iorelen's Camp, outside of The Rift of Nûrz Ghâshu
Balanced Dagger of the Mountains, level 59 and 63 - Best farmed in the later areas of Moria, possibly Lothlorien, and the later areas of Mirkwood
Beleriand Curved Dagger - An output from the Curved Dagger recipe hidden in Vermillion Scrolls, which are dropped by Draigoch. Dagger of Keria - Reward from the Epic quest 1.13.11
Blade of Swift Stings - Bartered from the Limlight Gorge reputation vendors in Stangard Morgul-steel Dagger - The_Ash_of_Gorgoroth quest gives you this dagger to deconstruct, but you can wardrobe it before using the Flame of Ancalamir.
Bognagol - Bartered from the classic skirmish vendor under the "Helegrod - Treasure" category
Dagger of Endurance, level 56, 60, and 64 - Best farmed in the mid-level areas of Moria, Lothlorien, and the later areas of Mirkwood, respectively Dagger of Stamina, level 58 or 62 - Best farmed in the late areas of Moria and the early areas of Mirkwood, respectively
Dagger of Stone-cutting, level 56 - Best farmed in the mid-level areas and instances of Moria
Malledhrim Dagger of Defense or Warding - Outputs of the Malledhrim Dagger reputation recipe