Any dynamic language - by definition, they check types at runtime. Or, unfortunately, a lot of static languages. Any static language that allows type casting,

Any dynamic language - by definition, they check types at runtime. Or, unfortunately, a lot of static languages. Any static language that allows type casting, for instance - that's the only way they can check whether a cast from a type to one of its descendants is valid (eg, in Java, casting an Object to a, say, URL).