Exactly how big is it? How big are you trying to make it? Floppy sized or email sized?
Take out transitions. They are annoying, hardly functional, and waste space.
Kill clip art. It's uneffective. It's like putting sprinkles on a wedding cake.
You could divide into multiple presentations if there is a good point to do so. Having a 120 Slide PPT is dumb, especially if you change subjects enough to stop the train of thought. If you are stopping someone's thought pattern, then it won't hurt to stop and open a new file.