Assume you generate a numbers with a pseudo-random generator, and print them, each one, to card. 

Now you take those cards and shuffle mounting a deck.

Are the numbers on the deck truly random now?

The idea is to produce inside a block of material two tubes, in the size of an atom. The tubes meet in a certain point of the material, with a precise angle. 

By feeding the tubes with the correct atoms, you can perform a perfect chemical reaction. It would be 100% effective. There would be no waste or excess of reactants.

Replicate such units to get more volume and you have a neat chemical plant. 

Building an atom-size tube, however, is not an easy task.

Naive.

The STM (Scanning Tunelling Microscope) allows for precise positioning of individual atoms in a substrate.

This is an idea to build multilayered constructs: you build them over material that sublimates, then stack the layers and wait for the substrate to disappear.

How different is ice that was formed under magnetic or electrical fields?

This idea once had my un-divided attention.

STADT starts with mapping a city as it is now, every business or residental lot. The business are carefully categorized, with the goal of placing competing business in the same group.

Let's focus on a single business: drugstores, for example. 

A complex formula would calculate influence of a drugstore on a certain plot. It would translate the idea of having a drugstore nearby or not. This formula would be made up, but would take into account the area of a drugstore (m2) and the distance from the drugstore to the place. The residential plots, when nearby, would give a bonus to the formula (I'll explain why in a minute).

Summing over all drugstores in the city, you would have the presence of drugstore services in that place.

The idea is to repeat this calculation all over the city or at least the lots you know to be for rent or sale.

What this would indicate is the best places in town to open a new drugstore. This works best for business that are more local, where people are not willing to travel too far for them. Hypermarkets, for example, work on much greater distance than grocery stores.

The residential plots would give a bonus to the formula because they would make the place attractive for new business, because of the customers. They would serve as an attractor. In fact, when I first worked on this, I separated low density residential zones (houses), medium density (small buildings) and high density (skyscrapers).

The company based on such ideas would sell the consulting services: people wanting to open business would seek them out for the information.

It is a great idea, but it is far from being a small one. At first I considered raising information about the lots of the city using Google Maps, but I soon found out it is an explicit violation to their terms of service. There is not such thing as a free meal.

This would be for artists.

It is a pen with three ink tanks, a red, a green and a blue. You would could change the ink mix ratio coming out of the pen, and make its trace any color you would like.

Apparently people tried this a kickstarter, and it wasn't sucessfull, to my knowledge. I'm afraid the reputation of this idea got a little tarnished after that.

In the first design, three flexible parallel tubes would go from the tanks on the top of the pen to the tip. There, the ink would mix before being transfered to paper by a sphere, like in a ballpoint pen. There would be three screws compressing each one of the tubes, in a way that when loosened, they could control the proportion of each color.

In a second design, more complex, the screws would be inclined, say 75° towards the body of the pen, and closer to the tip. They would not compress a flexible tube in this case, but would have magnets on their tip, inside the pen. These magnets would be close to a sphere, somewhat larger, and the ink would pass though the laterals of the sphere, between the sphere and the pen border.

In the rest position, the three spacings where the ink would flow would be the same and the same proportion of ink would mix: the pen is black. When you loose one of the screws, the sphere is displaced, closing more one side while opening the other, what changes the proportion of ink, and hence the color of the pen.

I suppose the first idea is better now that I've written this.

This would be a magnetic powder that could easily change the color of a car. it would be a little hard to remove, I suppose.

I've always pictured the colors as iridescent, like bug-color. 

Imagine that you have a window. On top and bottom of these windows, there are contact tips, for high voltage discharges. You discharge the tip producing an arc from top to bottom (or bottom to top). Then you discharge next one to the right, and the next, and keep dicharging them sequentially. When you reach the last tip on the window, you start all over again from the left.

The thing is to discharge them fast enough as to produce a wall of discharges. 

Would that separate the gases on both sides of the window?

At the very least, noone would be crazy enough to go through the window while this "shield" was on, althought it might be a really expensive fence.

This is very wild idea, for very little it didn't fall into the Lesser Ideas.

Study how kidneys filter water, so you can produce a dessanilization process that works with kidney cell culture.