Playing Spain, I'd say them as well - Portugal/Spain, Tomata/Tomato, perhaps for the slightly better units Portugal have . . . Looking at who continually keeps wooping the arse of all the other facrtions I must say Denmark! They have some wickedly strong units and that seems rather obvious to me, as in every campaign I've fought they're doing absolutely amazing AND they have a nice starting position - once they've taken Norway, Sweden and Hamburg, there's only one place to maintain troops . . .
Being Danish myself I love all these Danish units, even though some if not even most seem fairly historically inaccurate (I've had extensive Danish history and never heard of Norse War Clerics for example - there may have been one or two, but whole armies!) . . .