You can give yourself any genetic disorder

You can also get rid of them so don't worry about that. The only requirement is it has to be real for at least 1 individual

You might wonder "how would this be useful?" And well, there are certain disorders that would be actually insanely useful

For example some people have an insane metabolism, which makes weight loss a thing that takes no effort, you could eventually reduce myostatin production to tremendously accelerate your muscle growth. In case of blood loss, you can make your body go mad and produce it 10x faster. Disabling pain receptors is also an option. You could even make your body grow an additional pair of arms that you can freely control

It's just that whenever you activate a mutation, it will take your body a while to adapt to it. If removed, grown body parts will slowly shrink in a painless way