I am a big fan of the 6.5x43mm (.264 USA/.264 LICC).
I talked to Troy Laughton for a bit on it, and that case is super neat in that the projectile diameter can be easily manipulated to allow everything from 6mm to 7mm projectiles, and handle a wide variety of possible weights depending on the application. It also has adequate powder capacity to allow loading to under 6.8 pressure while still getting adequate velocity to do what it needs to do.
Low perceived recoil, minimal change to the size and weight of the system.
Arguably the best infantry cartridge that exists.
I am, however, apprehensive that the cartridge will get real traction. I really hope so, but without a good US domestic commercial interest, it will likely struggle to get adequate support.