For stereo RCA patch cables, Mogami w2965 and Rean NYS373 plugs, with a little heat shrink, will look like a professional cable. This is "dual coax" wire, so it look great when you need to run two wires (left and right). Redco sells it by the foot.
For mono RCA cables, including for SPDIF or a subwoofer, Mogami W2964 looks good. Redco sells it by the foot.
Belden 1505A RG59/20 is also a fantastic choice for RCA interconnects, as well as for digital coax and subwoofer LFE. Markertek sells it by the foot.
Good article from Belden about what wire is good for what.
Summary of choices:
Van Damme Pro Grade Classic XKE Pro-patch cable has also been recommended (Bare silver plated ultra pure oxygen free copper wire).
Update: A good friend commented: Mogami: "soft and warm". Belden: "RG stuff is not so hot". "Silver plate over copper is usually worse sounding than silver for some reason". He recommends https://www.venhaus1.com/diysilverinterconnects.html
Some interesting wire on AliExpress:
I have no idea if the quality of the wire is any good.
Note: 19 x .12mm is about 23AWG (I think). 23AWG times 2 is 20AWG
Fancy wire