For me:
Flash - Interactive media creation with moving elements.
After Effects - Superb motion graphic composite app. (2D and 2.5D NOT 3D)
Combustion - also a composite app. But I find it limiting in some ways.
Apple Motion - Native motion graphic app. for mac with good intergration to pro apps from apple.
Apple Shake - High end VFX composite app. and my new baby ;-)