closures, prototypical inheritance, the syntax for object/array literals. and I know it's not strictly part of the language, and it's deeply unfashionable to say so, but I'm quite a fan of the DOM, too.

Closures and literals are pretty basic things for many languages and very well-known.

Prototypical inheritance may have gotten much more exposure via JS, but I'm not overly impressed with it, and I hardly think it makes up for the rest of the language.

fair enough; JS introduced me to closures, so I'm a bit biased.