Just do :
ls -1R -I"?" -I"??" -I"???" -I"*[!.][!r][!a][!r]r]" You don't need grep at all.
NOTE: The above works... except it still gets at least afile-rar and I don't understand why. I'll leave it here, but I'm not proud of it. In any case, as others have said:
find . '*.rar'