Not only did the Den of Geek assemble a respectable (if not a little controversial) list of the top 50 special effects shots of cinema, the site also explained the tricks behind the illusions.
Of course the well-deserving staples show up in the list (Star Wars, Tron and Jurassic Park), but there was one in particular that I didn't know about, and it may be the most convincing moment on the list.
In Total Recall, there's a brief moment when a secretary changes the colors of her nails with the tap of a wand. How did they do it? The illusion was created through rotoscoping, a layered matte animation in use since 1915.