So CodeSearch, Critique, Borg, Sherlog, Cider come to mind as top notch tools that are not available outside. As far as libraries go, the C++ Fibers thing is incredible and I don't think it's open.

Blaze is amazing (albeit a bit slow) but Bazel should be more or less the same, haven't used it. Dremel, Spanner, Tensorflow, Proto, grpc are all available outside. Abseil (https://abseil.io/) is a great library available to everyone.