Plockton. Not a grass strip, but I think it enters into the spirit of the thread.
No facilities at all, sign in and pay landing fee at the wooden box.
There's a 20 minute walk down into Plockton village (used as the set for the TV series Hamish MacBeth). The Plockton Hotel is our favourite hostelry in the village. It's on the harbour front and has a superb menu including fantastic seafood.