7.65x53 Mauser. Nowadays I can buy new brass from Norma, but there wasn't any when I first got the rifle. Now I'm used to forming them from .30-06.
"6.5 Ross", basically a .256 Mannlicher rimless, except using rimmed .303 British brass. I made it to feed through a Ross straight-pull action that was already set up for .303.
I'm working on a ".311 Whisper", basically a .300 Whisper, except with a longer neck to cover the grease grooves on a cast bullet, and in .311 because I have several new .311 barrels on hand. I still need to finish the chambering and die reamers.
The .311 will have no ballistic advantages over the .300, it just suits my hardware and purposes a bit better.
Neither of the two above are really wildcats, they're just adjustments to fit circumstances.