The Hydra gets a lot of attacks, but I don't see any SQ's that would transfer over to its undead form. It gives me the feeling that the whole (ex) abilities in the Special Qualities line is a little inconsistent. The hydra gets an attack per head at no penalty, but no corresponding Quality that mentions it. (It still gets the attacks as an undead, because it of its regular Attacks entry.) The Ettin gets an attack per arm because each head controls an arm, but its has Superior TWF listed as a Quality. If you removed the Quality from the Ettin but left the Attacks line unchanged, it wouldn't really affect anything. (Its slightly weirder for the zombie versions. The Hydra gets a bite per head on an attack action, even though it has no listed SQ. The Ettin, which does have an SQ letting each head control an arm, still only gets one attack on a single action. Makes hydras great as zombies go.)
The Cloud Giant Oversized Weapon Quality seems a little odd to me too. Why not just give them the Monkey Grip as a bonus feat? It just seems odd to me that every Cloud Giant in the world can use an oversized morning star. Not gargantuan greatswords or axes, or maces. Just morning stars. (It reminds me of an old Kids in the Hall sketch about how in France everybody has just one spoon and if they lose it, they can't eat and they starve unless someone else wills them their spoon, except instead of the French its Cloud Giants and instead of spoons its gargantuan morning stars. But its a lot like that.)
Giants also lose Rock Throwing, since its a Special Attack. If they were proficient in throwing rocks, they'd keep the ability by the RAW, or if Rock Throwing were a Special Quality they'd keep it, but as its written I guess skeletal giants use the same improvised weapon ranges as anybody else who was trying to throw an appropriately-sized rock, instead of the 120' range increment sniper rocks they use in life. (My PHB lists the improvised thrown weapon range as 10', with no notation about size or strength of the thrower.)
One could interpret "Rock Throwing (Ex): Adult giants are accomplished rock throwers..." as Giants are Proficient in throwing rocks, and letting them keep the ability. (I mean, if you say that Rocks are Improvised Weapons, and giants are using them without the non-proficiency penalty, they are technically proficient in rock. Or they're not non-proficient.) Its kind of an end run around the otherwise unambiguous "A skeleton or zombie retains none of the base creature’s special attacks", but I can see the logic behind it. (As a GM, I'd say they'd lose it, but I can see someone going the other way on it.)
