At one point when I was lamenting the woes of being a green mage with a friend of mine, he pointed out there were black cards that brought back creatures from the graveyard, and no matter whether they got there by being countered or killed, I could get them back
Excalibur is the kind of card that just gets better and better
Do note that you cannot save yourself or protect yourself from colorless damage, so something like a colorless flyer such as Steel Hellkite will prove a problem, or colorless targeted removal like Scour from Existence or Karn Liberated
This isn't a Frequently Stated Comments
There are also a few cards that openly break the color pie, so youll occasionally be able to find a great removal spell in an unexpected color
At this point, we can go one by one and see who fits the decks vision