One of the craftiest specialist I've seen is the pirate. He can steal gifts, take back specialist lost in sub to sub combat, and is a key factor in most Queen killing strategies. He can also be used for his speed boost when paired with a Navigator to lock onto a sub near an opponents outpost before switching targets to the outpost.
One of my favorite examples of this was when someone by the name of Aesynil had only one base left, but he used some insane combination of Generals, Saboteurs, a Pirate, and a Navigator to slowly weasel his way all the way through the second strongest person's bases. Eventually, he trapped the second strongest person's queen in a Navi-Pirate sub trap. After that, Aesynil got a Hypnotist allowing him to take his vanquished opponents King and the mine it sat on. Aesynil finished that match in third place.
Zyxe? Now that is a name I haven't heard in a long time.