# C, 5 characters

 main;

It's a variable declaration - `int` type is implied (feature copied from B language) and `0` is default value. When executed this tries to execute a number (numbers aren't executable), and causes `SIGSEGV`.

[Try it online!](https://tio.run/##S9ZNT07@/z83MTPP@v9/AA "C (gcc) – Try It Online")