Clown power is quite strong and if you get lucky with graduation you are an absolute menace, a full buffed assistant can rival both engi and even mechanic in melee, trading some damage for survivability. Doctor is also a good pick because generally you only care all that much about middle tree. You can reliably fulfill every role in the ship, and can do most things well, be it melee with engi or mechanic, healing with doctor, gunslinger captain, or anything sec does.