Firestone came out with radioactive spark plugs in 1940. The idea was that radioactive material (polonium) would improve the electrical conductivity of the spark plugs, resulting in better fuel combustion. More details from the Health Physics Historical Instrumentation Museum:
Other than the slightly improved performance when the plugs were first installed, their benefits were questionable. The short half-life of polonium-210 (138 days) meant that the enhanced performance was only temporary. It also put dealers in the uncomfortable position of having to decide what to do after unsold plugs sat on the shelf for extended periods. Furthermore, the inevitable accumulation of deposits on the surface of the plugs’ electrodes as the vehicle burned fuel would attenuate the alpha particles and prevent them from ionizing the gas.
In 1952, in response to growing concerns about the safety of cigarettes, the Lorillard Tobacco Company introduced Kent cigarettes, boasting that they contained a "Micronite filter" developed by "researchers in atomic energy plants".
Turned out that the key ingredient in the Micronite filter was asbestos. From wikipedia:
Kent widely touted its "famous micronite filter" and promised consumers the "greatest health protection in history". Sales of Kent skyrocketed, and it has been estimated that in Kent's first four years on the market, Lorillard sold some 13 billion Kent cigarettes. From March 1952 until at least May 1956, however, the Micronite filter in Kent cigarettes contained compressed carcinogenic blue asbestos within the crimped crepe paper. It has been suspected that many cases of mesothelioma have been caused specifically by smoking the original Kent cigarettes.
Science-fiction author Cleve Cartmill is best known for his short story "Deadline," which appeared in the March 1944 issue of Astounding Science Fiction. The story isn't famous because it's a good story. Cartmill himself described it as a "stinker." It's famous because it contained specific details about how to make an atomic bomb — details which Cartmill somehow knew over a year before the existence of the bomb had been revealed by the U.S. government.
When Military Intelligence learned about the story they freaked out, fearing a security breach, and launched an investigation. They questioned Cartmill, as well as Astounding editor John W. Campbell. But eventually they concluded that Cartmill had gained his info, as he insisted, from publicly available sources.
However, the rumor is that Military Intelligence bought up as many copies of that issue of the magazine as they could, to prevent its dissemination. Which makes that issue quite valuable. For instance, at Burnside Rare Books it's going for $400.
Sometimes vendors would like to sell relatively high-value items in vending machines. That is, merchandise worth more than a candy bar. Nowadays that's not a problem because there's technology that can scan paper currency or read credit cards, making larger transactions possible.
But back in the 1960s, vending machines relied on coins for payment, so selling high-value merchandise wasn't practical. Especially since the machines could only measure weight, shape, and size to determine if the coins were real — and these characteristics are easy to fake with low-value blanks.
The British printing company Thomas de la Rue devised a solution: radioactive vending machine tokens.
Its researchers realized it would be possible to create tokens made out of layers of radioactive materials such as uranium and carbon14. These tokens would emit unique radioactive signatures that could be measured by Geiger counters inside a vending machine. Such tokens wouldn't be easy to forge. The company patented this idea in 1967.
I'm not aware that any vending machines accepting radioactive tokens were ever put into to use.
I imagine they would have suffered from the same problem that plagued other efforts to put radiation to practical, everyday use — such as the radioactive golf balls we posted about a few months ago (the radiation made it possible to find the balls if lost). The radiation from one token (or golf ball) wasn't a health hazard, but if a bunch of them were stored together, then the radiation did become a problem.
On May 5, 1955, Lawson was dubbed "Miss Cue" in reference to a series of nuclear tests conducted by the US military under "Operation Teapot," and publicized as "Operation Cue" in a short film distributed by the US Federal Civil Defense Administration. 
The day before the test, [atomic physicist Ted] Taylor rode the elevator to the top of the tower to view his device and to catch a glimpse of the equipment display scattered across the desert below. Nearby, a technician worked to clear a conduit pipe; a rat had somehow managed to wedge itself inside, threatening to ruin the shot. A break in even one circuit, regardless of how minor, would scuttle the detonation.
While Taylor was waiting, he managed to locate a concave, parabolic mirror. After determining the point at which the light would converge, he attached a small wire. The next day, June 1, 1952, he would conduct an experiment of his own.
At 3:50 on June 1, the troops in the trenches were told to kneel and lean against the side of the trench nearest the tower. Five minutes later Scorpion/George ignited with a force of 15 kilotons.
At the Control Point, Ted Taylor aimed his parabolic mirror at the intensely bright, fissioning mass. At the end of the wire he had attached a Pall Mall. In a second or so the concentrated, focused light from the weapon ignited the tip of the cigarette. He had made the world’s first atomic cigarette lighter.
It would have been better if Taylor had first radioed the control tower, "Hey, you guys got a light?" and they radioed back, "Sure." Then detonated the bomb.
A 1955 DoD film demonstrated the concept, without using an actual atomic bomb:
Sep. 10 was the 50th anniversary of Project Rulison, which was an underground nuclear test conducted in Rulison, Colorado. Its purpose was to determine if a nuclear bomb, detonated underground, could be used to release natural gas.
The answer was, not really, because the bomb will radiate the gas, making it unusable.
"There was this great rumble, and we were lifted about six or seven inches off the ground," he recalls. "There were a whole bunch of tremors reverberating through the ground. People down below described seeing ripples flow through the earth, like a rock that had been tossed in a pond."
Paul Di Filippo
Paul has been paid to put weird ideas into fictional form for over thirty years, in his career as a noted science fiction writer. He has recently begun blogging on many curious topics with three fellow writers at The Inferior 4+1.