I have many saves, and many favorites. If I had to pick one, it'd be Bound Bow. My main RP save, (and avatar) Dreadfall uses an unsmithed Skyforge Steel Greatsword. (It's got the highest damage/weight ratio, much like Elven Armor) If you do Smithing, it can also be ground up to stupendous with just the Steel Smithing Perk if you wanted to take the Light side up to Dragonscale, for instance. (Use Foresworn Armor for training, you'll run out of level before you run out of Foreswore.)
My favorite Daedric (By way of the Dwemer) weapon is Volendrung. In all TES games, but especially this one. It has a pulse, and gets the best comments from guards. A close second (In the Warhammer class, not Daedric) is the Longhammer, because it's not technically enchanted, grinds up with just Orcish Smithing, and can get one of the highest DPSs of all 2h weapons with Elemental Fury. (Or you can Enchant, and rename it.) Ironically short Reach, though.
In 1H, probably the Ebony Mace. It's tied for the highest base damage you can wield in 1H, absolutely gorgeous, by far the nicest looking weapon in the game, and can be Enchanted even nastier than the Mace of Molag Bal. Pretty much has to be Dual Wielded to get the striking speed up with an offhand dagger, though. My favorite enchantments on any weapons are Absorb stat (depending on the build, Stamina,and/or Health usually, ro Stam/Magicka for Nightblades) and Firey Soul Trap. The nastiest weapon I ever made was Bloodrust(c) a Daedric Warhammer with Absorb Health, and Firey Soul Trap. Slow as continental drift, but you rarely have to hit anything with it twice. Intended as an evil version of Volendrung.
For something a little different, I consider the Targe of the Blooded a weapon as much as armor. I mostly use Block to Bash, keeping them off balance so they can't retaliate instead of to simply soak up damage. Pairs incredibly well with Wall of Flames, so keep them stunlocked in the AoE, and stack Bleeding with On Fire DoT. Believe it, or not, I actually prefer Handaxes out of all the weapons, but there aren't any premade ones in the game so you have to DiY. Usually the Bloodrust enchantment, so the fire, drain, and bleeding stack with each strike. Very effective for a Spellblade.
. Got to say I love me stalhrim sword with frost enchant and soul trap;D
