Aloe

One of the easiest things to grow is aloe. In southeast Texas I helped water my great uncle in law's aloe green house. All he had in it was aloe since he used it for his stomach. Quite a few of the plante even flowered while I was staying there for the few short months. If you know someone who has it, all you need is a little starter plant and it will spread to fill the pot usually within a year.
As I mentioned, it's good for stomachs but it's also good for burns and cuts. A little aloe spread on a leaf of lamb's ear and you have a great bandage.
It can also be used to keep skin looking young after a bath.

It's apparently also very easy to kill aloe. All you need to do is leave it outside when it freezes for a few days and it all turns brown and dies... Fortunately I know quite a few people who have some and who are more than happy to share.