My favorite issue of this for all time is their life on mars issue. The cover showed an extreme magnification (using an electron microscope) of what was obviously a mutated fly (probably taken from some biology textbook), labelled as "images NASA doesn't want you to see" and the like. (This being shortly after the possible evidence of proto-bacteria in the possibly-Martian meteorite.)

That's not why this is my favorite issue, why I've kept this issue around for a few years. The reason is that there's a two-page exposé on the Y2K bug, giving all the hyperbolic sensationalistic hype ("planes will fall out of the sky," "everything with a microchip will turn on its owners," etc. etc.), with the most fucking hilarious inset image I have ever seen:

It was a picture of Bill Gates, with the caption "Mankind's only hope."