This is a question along the same lines as that in the thread asking what one magical item from the DMG would you choose to have in the real world, except that it deals with innate powers.
Well, little beats something like Wish at will, so please do not choose that. Preferably try to stick to innate qualities rather than spell-like abilities. Also, as nice as it may sound, try not to make up new ones, such as immortality, and stick to those that races/monsters in Core rulebooks already have.
Personally, I would probably choose something like regeneration or damage reduction (both set as high as possible, of course). Many of the immunities (energy types, poison, disease, etc), though, would also be nice.
Well, little beats something like Wish at will, so please do not choose that. Preferably try to stick to innate qualities rather than spell-like abilities. Also, as nice as it may sound, try not to make up new ones, such as immortality, and stick to those that races/monsters in Core rulebooks already have.
Personally, I would probably choose something like regeneration or damage reduction (both set as high as possible, of course). Many of the immunities (energy types, poison, disease, etc), though, would also be nice.