It's that little innate ability that is so easy to forget. And if you are one of the following 10 champions, you are happy that passives are easily forgotten. A passive can often mean the difference between life and death, and you will see this frequently from the 13 most powerful passives in League of Legends.

I originally intended on listing the 10 most powerful passives. But, it was just too hard to narrow it down to a top 10 and I wanted to avoid any qq'ing about Champion X not being on the list.

EDIT: Due to overwhelming response, I have added 2 more champions to the list, making it "The 15 Most Powerful Passives". Thank you for your comments on the forums and on Reddit :)