Sorry, I'm a jerk. I replied to the wrong comment.
I hate to pile on, but this comment is in error.
In one of Dana Scott's papers from the 1980s, he presents a programming language which is equipolent with Turing Machines but which consists entirely of the letter G. It's syntax was just the ability to apply expressions to other expressions, and it's operational semantics was some rewriting rules. It was very cute.