[Keeper of Dol Guldur]

What's betting that Hurin, a qualified elf-friend and hero of the first age was himself in possession of a fantastically crafted and razor sharp blade? Surely he owned a master weapon, something so sharp and quick that while a load of trolls was a lot to kill, no lesser man could do simply because their blades would turn like Boromir's did. How old was Narsil again? Forged in the First Age by Telchar, well maybe a few of the great men of old had the sister-blades to the Sword of Elendil (which presumably was once the sword of Elros, who likely either received it from Cirdan or it was passed from his father Earendil down from the armory of Thingol himself - a noted dwarf-friend (until the incident of the Nauglamir and the Silmaril, naturally).

Anyway, we know Beren had a knife capable of shearing through the Iron Crown of Morgoth to retrieve a Silmaril, and we know there were great elf blades in those days as well, Orcrist, Glamdring, Sting. It seems likely that the blades can attribute quite a bit to how well somebody fights something like a troll.

Trolls were bred in mockery of Ents. Ents are made up of the 'bones of the Earth' as Treebeard said(I think), and can rip through stone. Trolls turned into stone when the sun came out . . . but I'd think they had a very 'stony' nature regardless, as like to a rock as an Ent is to a tree. (maybe in 'corrupting' Ents Morgoth fed them minerals but no good clean water, possibly some venomous black magic, who knows?). Anyway, stabbing a rock isn't all that easy. Even stabbing a tree is hard, for anyone who has ever tried to drive a knife into a good healthy tree, more than a majority of blades turn. Sting, on the other hand, slid into an oak beam with ease, and so too right into a Troll foot. I wouldn't doubt that it could probably puncture good metal armor with a well placed and strong blow. I wouldn't be sure about the stone doors and walls of Khazad-Dum, which are covered in warding runes and the like, and the same goes for other 'enchanted' blades, rune inscribed, but a good sharp blade of elder craftsmanship seems to be the key in killing large amounts of, or extra-powerful enemies. Even Pippin and Merry's barrow swords were of fine craftsmanship of a bygone era, and slew some tough adversaries.