Suspense is vital to most writing--every story depends on at least a little emotional tension or there is no story. (Thumb your nose, guardians of the avant-garde.) Horror, thriller, and mystery fiction relies on suspense.
I showed my classes this wonderful clip from The Birds. While Rear Window, North by Northwest, and Psycho may have been better films from start to finish, this snippet reveals Hitchcock's masterful touch (and is pretty damn creepy, as well).
Suspense is all about waiting. You know something bad is going to happen, but the master makes you wait for it.