Returning to home airport from a local grass strip with another aircraft somewhere behind doing much the same. From his inbound radio call I had him positioned about 5 or 6 miles behind.
Making the 45° turn on to downwind I glanced over my shoulder and there he was, absolutely head on and seconds away! My avoidance was close to aerobatic half expecting his prop would eat my tail.
Back at the hangar we had a discussion. Despite no 'base', 'final' or 'cleared to land' transmissions from me or the tower he thought I was already landed. Nor had he seen me even though I was dead ahead and really close!