I had a .22-6mm (30° shoulder version) a few years back. It got rebarreled to .22-250 since both the original builder and myself insisted on pushing max loads down the tube and the throat was pretty well worn out after a few seasons.
A friend of mine currently has a .22 Cheetah (.22-243 or .22-308). It's a screamer if you max the loads too.
A 6.5-06 (regular or Ackley) build is on my bucket list too.