I may soon encounter a situation where player characters might sneak up on some sleeping giants and try to murder them or steal their coins, which are stored in bags near the sleeping giants.
Sneaking up on the giants is clear: Sleeping character gets +10 DC on perception checks. Coup de grace is clear, though a risky proposition against a giant.
Suppose, then, that the characters do successfully sneak to the sleeping giants and coup de grace one or several of them. What is the DC for the others to wake up, supposing the attacked giants are slain? Battle is DC -10, details of a conversation are 0, so presumably -5 would be okay, unless the weapon is terribly noisy (a gun, say, or a morningstar).
If the other giants do wake up, how quickly can they act? Should I have everyone roll initiative and go with that, or give automatic surprise to the player characters, or something else?
The other likely action PCs might take is to steal some coins from the giants. They have several thousands in total, so stealing all of that is out of question. How would one check if this makes enough noise to wake a giant up? I think this should be related to the number of coins one steals and how quickly one does it. Sleight of hand and stealth are likely the relevant skills here.
Best Answer
Going through the points;
Coup-de-grace
Coup-de-grace does not specify if the victim makes any noise if they fail their Fortitude save of 10+damage dealt (and thus die) however if they make the save then they certainly would wake up.
This then becomes a DM decision. I personally would make a second Fortitude save for the monster against the same DC with a modifier of the characters stealth bonus rather than the +10, which takes into account how good the character is. If this is failed then the victim expires noisily, this then gives others nearby a chance to hear/wake up.
Waking giants
The DC to use perception when asleep is +10, meaning a base DC of 20 to wake if they are asleep, modified - as you say - by noise of the weapon, once battle starts this is -10, which means a DC 0 to wake up.
Note: There is a lot of debate about battle at waking up on the pazio forums
If the giants wake up then they will be effectively flat footed and surprised for a round, the round thereafter they would roll initiative as normal and remain flatfooted until their go.
Stealing from giants
Stealing a small item from a sleeping giants body will be sleight of hand DC 20, the giant gets a penalty to detect this as they're asleep (+10). Stealing larger objects should, as you say, give a bigger penalty (although not covered directly by the rules). If the bag of loot is merely beside the giant then stealth should be used instead and the giant again makes a perception roll vs. this.
The standard coin weighs about a third of an ounce (50 to the pound).
Sizes and weights of monsters are listed here which gives you the weight of an person for small of "8-60 lbs" quite a lot really! But there's no weight modifier for objects as these are related to the size of the creature that is using it - ie a large sized dagger or small sized dagger for the creature wielding. Just a weight modifier for armour. (about three quarters down, "armour for unusual sizes")
This means it's down to your call; I'd scale it up with multiple -2 penalties for every 10 lbs they're trying to lift, which is 500 coins as they're more likely to clink clink clink.