tor

I use the www-client/torbrowser-launcher::torbrowser package.

Just run

sudo eselect repository enable torbrowser

then add

/etc/portage/package.accept_keywords/overlays

*/*::torbrowser ~amd64

/etc/portage/package.use/tor

app-crypt/gpgme python # required by torbrowser-launcher

Consider reading /var/db/repos/torbrowser/Readme.md