German postal hyperinflation reached a crescendo with two stamps (Scott #299 and #305) both denominated at 50 milliarde (50 billion) mark. These were, of course, the highest denominated stamps in their respective series, used for mailing packages and the like (at least until inflation overtook their value). However, the lowest denominations in those series were still an impressive 500,000 and 10 million, respectively.
Even worse than the Weimar Republic's hyperinflation was what Hungary experienced in 1946, when the highest denominated stamp (#774) was a dove and letter design with a printed value of 500,000 billio-pengő -- that's 500 quadrillion pengő! (A few years earlier, a comparable, high-end stamp would have cost only 80 fillér, which was less than 1 pengő.) The cheapest stamp in that series was 1 trillion pengő -- convenient for sending a postcard to Aunty Yllona! (Note that the Hungarian billio is in the traditional long scale, so it is equal to a modern trillion. They also printed three stamps, #757-759, in milliards, or modern billions, before inflation made even that unit impractical.)
Hyperinflation is especially interesting to philatelists, because due to the rapid devaluations of the period, some stamps were only in use for a very short time, and are now worth far more used than unused. Of course, fraudulent cancellations abound.