I'd give myself ability to go into comma where invulnerable. Just wake up when I feel better.

I'd give myself ability to go into comma where invulnerable. Just wake up when I feel better.

I... Don't understand how a heart failing would result in me being able to extract a higher water content from a fluid I drink without adverse effects.
Like being able to drink salt water without it being fatal.
It's a bad joke. Heart failure is defined by reduced cardaic output, i.e. the heart doesn't pump as much blood to the rest of the body. It's not so much that you extract water, but you rather you retain it because the kidneys don't get enough blood. The powerful diuretic, Lasix, is given to heart failure patients so they don't drown in their own fluid.
You do, however, already have the ability to extract water from various sources. The nephrons of your kidneys extract water from urine, and so can large intestines from your poop. Also, I believe water flows through the stomach mucosa. The nephrons of your kidneys also have additional hormonal regulation that extract water. It's called RAAS (renin-angiotensin-aldosterone system) which uses sodium ions to retain water. There is also the anti-diuretic hormone that comes from the posterior pituitary gland.
I think our ability to retain water relatively well comes from the fact human bodies evolved in dry areas in Africa.
/SCIENCE!
A more powerful and adaptative immune system should be awesome.
Faster metabolism if minor. For major I would go for teeth regeneration, I hate going to a dentist.And faster reflexes, not superhuman but kind of top human.