This only works if your set ussage is not resticted but it is great against other decks.
If something big attacks you, you can use diminish, let it go through, then no mercy will kill it. I love to use this combo wjen playing against a brute force deck.
{No Mercy} + {Diminish}
Don't forget to write the cardnames with curly brackets around them so the rest of us can easy enjoy your combo.
By-the-by, if you've already made their guys 1/1, why not just block them and kill them?
If you dont have anything bigger than a 1/1 then it works. If not then just use diminish then block.