I distinctly remember something somewhere that allowed you too ignore the heavy property on weapons. It might’ve been a feat or something else, but I think it wasn’t Homebrew. I’m not sure. Is this a thing?

So you could wield two greatswords, one in each hand, if you have this feat and the dual wielder feat?

I think there may have been something in 3e that let you wield a 2-handed weapon with 1 hand. But not in this edition. 

Quote from Xalthu >>

I think there may have been something in 3e that let you wield a 2-handed weapon with 1 hand. But not in this edition. 

 oh, thanks! dont know where i saw that then

Quote from MusicScout >>

So you could wield two greatswords, one in each hand, if you have this feat and the dual wielder feat?

 For what it's worth, the heavy trait is separate from the two-handed trait. The only thing heavy does is cause small/tiny creatures to have disadvantage when making attacks with the weapon.

In 3e, a Mithral weapon would halve the weight of the metal component of a weapon and I think perhaps, as it definitely did with armor, allow the reduction by one category of the effective size of your weapon.  I don't remember off the top of my head if they used heavy and light descriptors in 3e too, but they did do sorting of weapons by small, medium, large, huge etc.  There were a pair of feats that would let a halfling et al use a large weapon such as greatsword and a human et al use a huge one: the Fullblade, aka Ogre's Greatsword.  I think this was a first step in opening up anime style weapon vs body-size proportions.  5e, doesn't quite have anything like this in RAW, but at my table I would perhaps rule that a largely metal weapon; one whose metal component relative to it's wood component was at least 60% of the weapons composition (i.e. largely swords) comprised of Mithral would indeed reduce weight category by 1 step for the purpose of allowing creatures of different sizes to wield weapons they normally would not be able to wield.

Quote from Shepherd_Hubbard >>

In 3e, a Mithral weapon would halve the weight of the metal component of a weapon and I think perhaps, as it definitely did with armor, allow the reduction by one category of the effective size of your weapon.  I don't remember off the top of my head if they used heavy and light descriptors in 3e too, but they did do sorting of weapons by small, medium, large, huge etc.  There were a pair of feats that would let a halfling et al use a large weapon such as greatsword and a human et al use a huge one: the Fullblade, aka Ogre's Greatsword.  I think this was a first step in opening up anime style weapon vs body-size proportions.  5e, doesn't quite have anything like this in RAW, but at my table I would perhaps rule that a largely metal weapon; one whose metal component relative to it's wood component was at least 60% of the weapons composition (i.e. largely swords) comprised of Mithral would indeed reduce weight category by 1 step for the purpose of allowing creatures of different sizes to wield weapons they normally would not be able to wield.

 That was it, it was the size category thing I was thinking of.

You also can't use a Heavy weapon as a monk weapon.  Makes me feel like the developers had some terrible experience with monks during playtesting because they nerf them in strange ways.  Hahaha