Heavy (3.5e Equipment)
From D&D Wiki
"You grab the greataxe, hefting it up, but, not expecting the excessive weight, you lose your balance and fall flat on your face. The greataxe is much heavier than it seems."
Only two-handed weapons made primarily of metal (such as a great axe, heavy flail or a greatsword, but not a quarterstaff) can be enchanted with this enhancement.
When a weapon enchanted with heavy is used with two hands, the damage from your strength bonus is multiplied by 2 instead of 1.5 and because of the sheer weight of the weapon add 2 additional damage die that the weapon already does (example, a medium sized greatsword normally does 2d6 a heavy greatsword would do 4d6). However, any weapon enchanted with heavy also has a minimum strength requirement to wield correctly of 19 or greater or, if it already has a strength score requirement to wield, the minimum strength score requirement is increased by 2. Additionally, there is a minimum requirement of 16constitution. Finally, the weight of the weapon is increased by 100%.