I'd also add operator overloading, though that tends to go hand in hand with templates. The fact that I can write numerical code that works for say, any type that implements addition and scalar multiplication, is wonderful.

In Java, as far as I know, this would be utterly impossible, because implementation of interfaces must be explicitly mentioned. Even though Double implements addition and scalar multiplication, it could not be used in such a function because it doesn't explicitly state that it implements such an interface.