I'll also go with Vader as the most memorable single character introduction.
My award for best ensemble introduction:
Silverado. Four characters, four quick introductions showing the gunslinging style for each character.
When I first heard that a D&D movie was being made, I was really hoping that the director would copy this introduction format, with a quick scene for each of the 4 characters (fighter, wizard, rogue, cleric) to strut their stuff. Sigh.
-RedShirt