Does the merciful property on a weapon make any energy damage it does nonlethal as well? I have an idea for a halfling stun gun character
The weapon deals an extra 1d6 points of damage, and all damage it deals is nonlethal damage.
Don't just quote the ability, please. I've read it but I don't recall a rule anywhere saying that energy could be nonlethal. I'm just double checking to avoid any arguments for the future.
Chances are good that you'll just have to have your DM make a ruling on this. It certainly is easier to envision nonlethal electricity damage than, say, fire damage.
Just pointing out that the rules are so specific that I could not have said anything better. Now as to whether or energy can ever be nonlethal:
You can alter spells that inflict damage to inflict nonlethal damage instead. Spells that inflict damage of a particular type (such as fire) inflict nonlethal damage of that same type.