There is some prudence that needs to be taken when saving critters. Some things are near impossible to revive or are so challenging to keep that it's not even worth trying. I've saved a few coral but it takes a solid system and a watchful eye. However when it does end up working out it's exciting to see it progress and heal.
Here are a few that I got for cheap or free that survived-
Stylophora before (crappy pic but you can see the dead spot of the top)-

After (over 3 months I think)

Blastomusa before (it almost died completely but started sprouting new heads just before)-

After

So good luck and don't feel bad about trying to save coral, just make sure you do your homework before you bring something home.
Sculpin