Double dispatch is generally simulated with imperative languages via the Visitor Pattern. Generally used when you have objects that won't change their structure very much (and are backed by an interface of some sort [also needed for the polymorphism aspect of the pattern]), but have to do lots of various manipulations with them. That way, you don't have to change the interface each time you add another method. Also referred to as "inversion of control." I used it before for filesystem type objects and for walking over the structure of an XML file (though both times were for school related projects). I could probably dig up the labs and post them on my Github for anyone interested. It's pretty cool how it works (and sort of hard to wrap one's head around initially), but not something I would consider using often.

Scala has a unique take on double dispatch[1][2] for being a hybrid imperative/functional language.

[1] http://stackoverflow.com/questions/8618082/visitor-pattern-i...

[2] http://blog.nirav.name/2009/04/how-scalas-pattern-matching-c...