I think that is tough to call and may be different for each one.
For speaker cable I use Canare 4S11. Reasonable price and very highquality.
All my HDMI cables are Monoprice CL2 rated and are the diameter of my thumb. I have runs up to 25ft and never had an issue.
Analog interconnects I now make myself. I buy good quality RG6 and have compression connectors for both RCA and F-type. This way I can make them the exact length I want and it is always nice to make your own stuff.