Using this simple method, one can keep shaving razor blades sharp for many uses (around 150). This method is so far unexplained but according to my strong empirical evidence, works well! For a quick summary, check out the following video:
Amazingly, all you need is a smallish pyramid made from plastic. Our pyramid was obtained from a super market, and was initially used as packaging for Ferrero Rocher chocolates. It is shown in the images. This is a square based pyramid, not much bigger than your average Gillette shavers.
Wash the pyramid out with some form of bleach or disinfectant to make sure it is super clean. Then remove the razor blade from your shaver and place it in the center of the base of the pyramid. This is shown in the image. Here I have used a Mach 3 razor from Gillette.
Then align the pyramid so that the razor faces North. This is also shown in the video (so check it out if you need further clarification). Once this is done, close the pyramid and don't disturb it until you next need to shave. I have my pyramid in my bathroom, next to my sink. You will notice that I have 2 razors in the pyramid. Note that the total volume of razor blades should not exceed 5% of the pyramid (roughly) or it may not work well.
The idea that pyramids can be used to keep razors sharp is not new. This idea has actually been patented by a Czech inventor (use Google to dig deeper). Many have speculated about how this all works, but the most common explanation is that the pyramid dehydrates the razor blade, removing water molecules which make it feel blunt on the skin.
Make sure the pyramid is aligned to physical North, and not magnetic north. An easy way to do this is to see where the sun rises (East) and use this to orientate the pyramid.
Also, I am aware that this was presented on Myth Busters (was their pyramid aligned like this one?) and they busted it, but I am not claiming that you can take an old blunt razor and make it new. I am claiming that this method can be used to make blades last longer.