Bad toys. Really bad toys.

The worst! (Via John Hawks.) For example, there's the U-238 Atomic Energy Lab:

For a mere $49.50, the kit came complete with three "very low-level" radioactive sources, a Geiger-Mueller radiation counter, a Wilson Cloud Chamber (to see paths of alpha particles), a Spinthariscope (to see "live" radioactive disintegration), four samples of Uranium-bearing ores, and an Electroscope to measure radioactivity....

The toy was only sold for one year. It's unclear what effects the Uranium-bearing ores might have had on those few lucky children who received the set, but exposure to the same isotope—U-238—has been linked to Gulf War syndrome, cancer, leukemia, and lymphoma, among other serious ailments. Even more uncertain is the longterm impact of being raised by the kind of nerds who would give their kid an Atomic Energy Lab.

Hmmm.... yeah: What strange toys affected your young, impressionable mind, and how do you know the difference between the effect of the toy and the effect of growing up with the sort of parents who let you have it?

Strangest toy I was given and allowed to play with: a small paper cup full of mercury.