It is also with regret that I must confess my ignorance of him during his life. I've only begun taking notice of his name and seeing some of his teachings posted online (they've been there, but I wasn't looking). Venerable Master Maha Ghosananda was the Supreme Buddhist Patriarch of Cambodia, and was nominated four times for the Nobel Peace Prize. From what I've learned of him so far, he was an amazing, wise, and - most importantly - effective Buddha.
He died in Massachusetts at the age of 78. Here's a link to his obituary in The Economist: