Instantiator 
I want to be able to instantiate an arbitrary Ruby class without knowing anything about the constructor.
The initial requirement for this has come from my Introspection project.
Usage
class ArbitraryClass
def initialize(arg1, arg2, *other_args)
# stuff
end
end
require "instantiator"
instance = ArbitraryClass.instantiate
p instance.class # => ArbitraryClass