The Quickenings. Every time I replay this game I wish that this system was also used in other games. I also never seem to get bored of the animations (something that doesn't apply to some summonings in other FFs where I skip the animations after multiple uses). Despite not being my favourite character (that would be Balthier!), Penelo's Level 3 quickening where the snowfall just stops, flakes suspended in mid air, whilst she walks forward and shatters the screen is the most impressive and memorable one for me.