Lithium hydride
Before the Castle Bravo nuclear weapons test in 1954, it was thought that only the less common isotope lithium-6 would breed tritium when struck with fast neutrons. The Castle Bravo test showed (accidentally) that the more plentiful lithium-7 also does so under extreme conditions, albeit by an endothermic reaction.
Castle Yankee
Although it had been predicted to produce a yield of 6 to 10 megatons, it actually produced a yield of 13.5 megatons, the second-largest ever yield in a U.S. fusion weapon test. Like the Mike, Bravo and Romeo tests, a large percentage of the yield was produced by fast fission of the natural uranium tamper. Of the total yield, 7 megatons were from fission; the other 6.5 megatons were from fusion reactions. The high fusion yield was due to the enriched fuel and set a U.S. record that stood until Hardtack Poplar in 1958.