I love the appearance of fluid effects. When I was younger I used to enjoy dropping food die into water and watching it dilute. The following links are two scenes that really inspire me because of their usage with this effects.
http://www.youtube.com/watch?v=gGDM5svwFN4 -Dumbledore’s Army from Harry Potter 5 produce Patronus spells. The Patronus spells look like a fluid effect.
http://www.youtube.com/watch?v=VrVdCkKxty4 –Nightcrawler from the opening scene in X-men 2. Teleportation appears to use a fluid effect.
I really like how fluid appears to trail the animals produced from the Patronus spell in the fifth Harry Potter Film. How the fluid dissolves into the air behind the spell, and how they glow creates a beautiful appearance. Also I like how Nightcrawler from X-men would disappear and reappear. The fluid used with him wasn’t filled with as much motion as the Harry Potter scene but the effect had gave life to his actions.