Here is an interesting article from Astronomy.com: The Seven Best Travel Spots In Our Solar System – And How To Die There
The Moon — silicates are bad for you
Mars — chlorine salts are bad for you
Europa — Jupiter’s radiation is bad for you
Titan — actually not so bad, by comparison
Outer space — this is kind of a cop-out, isn’t it? Outer space, really? That doesn’t count. Come on, go back to real actual places.
Enceladus — Saturn’s gravity is bad for you
Ceres — actually, semi-okay! The article concludes, tepidly, “Certainly less out to kill you than Mars or the Moon.” Well, that’s a start.
Offhand I would suggest that the sensible thing to do is build enclosed environments in big rocks and park the rocks wherever seems best. Gotta block gamma rays and so on, so building your habitat inside a big rock makes sense. And that way you ought to be able to seal in the environment you want and seal out the environment you don’t want.
But I will be sad if we never get to say high to the aliens living under the ice on Europa.