The trick with using a GSword as a parry weapon is that you've got to get them to hit you while you're bringing the sword down, and you only get like 5 frames for that. So in PvP it's gonna be real hard to do that without predicting your opponent real well. Most people'll roll around and try to counter attack, so I suggest doing it about a second after they get out of their roll, you should immediately turn around and start to parry. And if you're lucky you'll land it. Also fun facts, you [b]cannot[/b] parry standing 2handed light and heavy attacks from the Mastodon Halberd and all Ultragreatswords Great Hammers and Great Axes. However you can parry their dash attacks and roll attacks.