You're in luck cuz he wrote a whole book about it called JavaScript: The Good Parts. It's a good read.
But I don't care about the good parts.
I'm asking about the bad parts.
I guess I should have been more clear that he talks about the bad parts in the book in order to tell you what not to do.
I find automatic type coercion to be the worst one. Everything else is fine.
Javascript's combination of default global scoping and automatic instantiation of variables is another bug bear. It's too easy to unintentionally shadow a variable or in combination with automatic type coercion get bugs that are really hard to track down.