The A-Bomb
My favorite part is the bomb, itself. The most notable parts of it are: a telephone keypad; a VW ignition switch & key; salad bowls (that always made me laugh!); and for power....Duracell batteries!
Also, the scene where Paul is actually building it: the camera pans over a table of parts & I could clearly see a few of those old Radio Shack "Supermarket of Sound" packages. I could just picture him going into RS:
Clerk: "My, you're buying a lot of electronic parts. What are going to do w/ all this stuff?"
Paul: "Oh nothing much, just my science project."
Clerk: "Oh? What are you making?"
Paul: "Just an atomic bomb."
Clerk "..." o_O
Finally, I always wondered what would have happened if Paul had actually unveiled the bomb at the science fair! A mass panic?