.223, unless you are in a rimfire only area. In those areas the .22WMR and .17HMR both have there places. I use a .308HB for a varmint gun at times. 120gr handloads shoot well. For a .223, I really like the CZ527. It has a 1:9 twist heavy 24" barrel. Plenty for up to 65gr that I've shot, rated for 75gr. It is so accurate it is kinda boring. It has a CIP chamber, so Nato 5.56 is no issue. If you want to make a statement, it does it flawlessly.
Freedom is not free. The best of us always leave too soon.