Always thought the .280 was a good one. Loraine Keith had one that Elmer had converted to what he called duplex loading, that simply had a tube running up to the top of the powder charge from the flash hole. The powder was ignited at the top, rather than at the bottom as normal.
The Improved case kinda lit my fire, same as the 7x57 IMP.
OOPS - time to go to the gym.