A half-circle gate latch. Closed.
And now open.
There is not much to this simple device. It may not be able to endure vigorous attempts to break it open, nor is it as quick to slide open and shut as some latches, but it is a different take on a standard mechanism. It is also more aesthetically pleasing in my opinion.
Can one be pleasantly surprised by a lowly gate latch? It seems I can.