[He doesn't even need to consider the question, he already has his answer:] Zangetsu. He's exceptionally irritating at even the best of times, and his unpredictable nature is likely to be a liability for us all.

[That's entirely true, but it's also at least 60% because of the Pizza incident. He's still very angry about the Pizza incident.]

Though Rideaux is and always will be my first pick.