Create custom property with drop down menu connected to associated contacts

[treygriggs]

I'd like to create a custom property (i.e. Billing Contact) that allows me to select this contact from all associated contacts on this record.  For example, if there are five contacts associated to a Company record, I'd like to be able to select which one is the Billing Contact in a separate custom field.  

[AMorfey]

Seconded - association labels is not a great feature and being able to use custom drop downs that link to objects in the left hand information panels would make a huge difference