Pike: You probably know about the pike's charging attack, that deals three consecutive hits in a straight charge, but the hitbox changes when 1h or 2h. When 1h, the hits start shortly after you hit r1, specifically the moment you lower the weapon. When 2h, the hitbox doesn't start right away. Your character lowers the pike, hunches over in a double-step, then charges, starting the hitbox.
Halberd: The 2h r1's animation ends a tiny bit faster if you connect with your hit, making a landed hit harder to punish than a missed one.
GSoA: Due to its length, I think this is the only GS that this can be done with. The 2h (haven't tested 1h but the hitbox seems smaller to me) running r1 can hit twice when running past the opponent to your right. It hits once when next to them, and the very backswing, the very last tip of the attack, can hit the opponent again if you have the perfect angle and are facing the right direction. Note that I've only pulled this off against mobs and not very often.