I remember reading somewhere last year that arcgis 10 would allow the creation of animated markers (alike animated .gifs) that could be either exported to pdfs or seen inside arcmap.
Does such feature actually exist?
You can Export animated markers [.bmp.jpeg] with the "Exporting an animation as sequential images"
But to have animated markers inside ArcMap - No. Though you could try loading in an animated gif as a map marker.