The first electronic digital computer took up an entire room.
ENIAC (Electronic Numerical Integrator and Computer) was completed in 1946 and cost $400,000 to build. The US government used it during World War II to perform calculations for the construction of a hydrogen bomb.
#10 An old choir director of mine lived next door to one of the guys who developed the earliest patents for home microwave ovens. They were approved and being marketed by the 70s, but he wouldn't have one in his house until the 90s because they still leaked too much radiation of some sort.