I learned of this via thedailywhat here on Tumblr, but I think it’s deserving of it’s own little place.
To sum it up from viralviralvideos.com:
Sadly, after already two heart transplants, 17 year old Australian Wilson-Miller was told by his doctor there was no more they could do, and that he didn’t have long to live.
After hearing the morbid news, Wilson set out to make a private video to be shared with his social networking connections, but accidentally posted the video to the public realm. Now, his powerfully touching and emotional message has gone viral, amassing over 1.3 million hits.