The famous JATO Rocket Car story was one of the original Darwin Awards winners but has now been debunked as an urban legend. It was originally circulated as forwarded email.
This legend was again convincingly debunked in 2003 on the Discovery Channel show MythBusters. They replicated the scene and the thrust of the JATO with several commercially-available amateur rocket motors. The car did go very fast, maybe 150 mph (240 km/h), but did not go anywhere near 300 mph (500 km/h), and did not become airborne.
This is the text of what appears to be the most popular version of the message, judging from usenet repostings:
The original Darwin Awards were ficticious. Both were contained in a 1990-12-07 Version posted to rec.motorcycles of the JATO Rocket Car urban legend. When this urban legend was debunked, it was specifically pointed out that the mentioned Darwin Awards were ficticious. It contained a reference to the 1985 mention of a Vending Machine Tipover Darwin Award. It may have been Paul Vixie who wrote the introduction to the JATO urban legend that first included the term "Darwin Award" (if the message header was not forged) who is most responsible for the spread of the term. Vixie credits Charles Haynes with making the (informal) Darwin Award Nomination, but it was Vixies specific wording, with the first sentence crediting Haynes stripped off, that was actually circulated and actually refered to the Darwin Awards as if they actually existed and were common knowledge, though the message wasn't widely circulated until it was reformatted. It appeared to remain fairly dormant (asside from a request for reposting) until 1995, when the message surfaced again in rec.pyrotechnics but this time the email header was stripped off the introduction, though the main story is still indented. Three days later the introduction is fully integrated into the story and it appeared on rec.humor in a form that made it a truly infections meme. There is evidence on google groups that as soon as it was reposted in 1995 it quickly began to spread, being posted on usenet 24 times within the next month. In 1996 the legend was further embellished with references to the year of manufacture of the car and G-Forces and to the form which showed up in my mailbox 1-1/2 months later (55% of all postings on usenet which included "JATO Rocket Darwin Award impala" also included "g-forces"). Though this urban legend had apparently been around long before 1990, it appears to have been the addition of the Vixie Darwin Award introduction and the subsequent two edits to integrate that introduction and then posting on rec.humor that may have boosted its meme status and the 1996 embelisments increased its popularity up to twofold. Popularity peaked around the end of 1996.
The Cult of the Dead Cow, a well-known hacker group and ezine, published an extensive elaboration in 1998 that in a detailed and plausible manner attempts to explain the most common details of the Rocket Car legend. Four adult males under 25 engaged in assorted illegal activity, welding, drinking, Rube Goldberg engineering, and scouting to build the rocket rail car when they happen upon JATOs in a junk pile. After a lengthy and well-written history of the car's planning, group dynamics, secrecy and construction, "CarInTheCliff" describes with an entertaining tone the car's only test in such a manner as to account for all the elements of the circulating legend plus the elements he has added while discouraging repeats by example.