Tough to pick a favorite, there are so many that I like but for many different reasons. Black Hole as someone mentioned above is hypnotizing.
I have not yet played Iron Man, and I think the movies are ok. But the sound package on that pin just grabbed my attention immediately when I heard it at Allentown it sounded great and it was loud.
I picked Shadow out of above, LOTR a close second.
I think Scared stiff would be my favorite.