Ah, the fabled Argonian posion immunity, envy of the other races. Such a wonderful trait, to be able to go through life only needing to worry about a bandit's blade and not what may be coated on it, walk into a room traqed with poison gas with impunity, to... Oh, it's gone. Okay then, what takes it's place, like a 75% resistance or 50% or what? ... A once per day 60 second health regeneration? You're sure? ... Well, okay then.
Local waterways
All the rivers make for good overland highways, even if only one way because of the current and waterfalls every 30 feet (which are quite fun to go down). Being able to jump two hundred feet into seven feet of water and be fine is great for making a quick getaway... as long as your sure of where your jumping from, or rather where your jumping into. But being unable to use any weapons or spells underwater turns the normialy mostly harmless slaughterfish into something of a nuisance that can ruin an otherwise pleasant swim below the ice flows.