Similar to the Dardick, but much older- the .307 Schneelock Triangular Revolver Cartridge (no, really, I could not make that name up!)
Shown in Winant's Firearms Curiosa, the charge holes in the cylinder were triangular rather than round. Shape was sort of like cutting an orange in half, and looking at how the sections fitted into the round orange. Bore was triangular, rotating on its axis to spin the bullet. Find a copy of Winant's book- more weird guns than anything I have seen.
There have been revolvers with superposed loads (Walch 12 shooter- 2 loads in each charge hole- fire front load, then rear) and the Lemat- upper barrel for pistol bullets, lower barrel was shotgun.
And the Gyrojet Rocket pistol- cartridge was a solid fuel 45 cal rocket- hammer struck nose of bullet, driving it back on a fixed firing pin.
PS- I have ONE reproduction Crispin cartridge. Weirder than socks on a rooster!