I know this is snark, but there’s an arguably good answer. That’d be Lisp, according to an essay by pg that I’m too lazy to dig up right now. (Probably “revenge of the nerds” or something.) You just write the language in the parse trees.
arguably FORTH has even less syntax
Brainfuck and Piet come to mind... come to think of it, brainfuck compilers might get mad about unmatched brackets. You can't go wrong with Piet, though.