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Undefined
Undefined is a programming language that,
Turing-completeness
A standard-compliant Undefined program is both capable of simulating a universal Turing machine and incapable of simulating a universal Turing machine, and can also do something a Turing machine cannot do. But the language itself isn't Turing-complete, because it has zero of such programs.
Practically, the Turing-completeness of this language depends on the implementation. Some instructions might consistently form some kind of control flow in some interpreters.
Interpreter
Every program in your computer is an interpreter of Undefined, and all of them are bug-free. This may debunk the myth that every program that is complex enough always has bugs.