Actor Charlie Sheen and American exchange student Amanda Knox made headline after headline this year for very different reasons. (Steve Granitz/WireImage|Franco Origlia/Getty Images)

The antics of a Hollywood star, an explosive murder trial overseas, the hunt for a mysterious attacker, a harrowing survivor's story and a beloved pet's time in the sun topped the "20/20? list of most popular stories of 2011.

Which story is the most unforgettable of the year? Read the list below and then vote.

1. Hero's Sunbeam: The night before he died, soldier  Justin Rollins and his fellow platoon members played with a litter of stray puppies in an Iraqi war zone. After his death, Rollins' family and girlfriend staged a battle of their own to bring one of those puppies to the United States. The  Rollins family's successful effort to bring the dog - later named Hero - to their home drew national attention. But viewers weren't just touched by their heartwarming story - they were also amazed at a photo captured by a 20/20 producer, who happened to be at the right place at the right time when a  beam of light illuminated Hero in the Rollins' backyard.

2.  The Suitcase Clue: After cruise line worker  Inna Budnytska was assaulted and left for dead miles  from her Miami hotel, investigators were stumped. Despite the hotel's surveillance cameras, there was no footage of Budnytska leaving the hotel, much less leaving the hotel with a potential suspect. When private detective  Ken Brennan scoured the footage, he noticed a man carrying a suspiciously heavy suitcase. It was a clue that would break the case wide open.

3. Sheen's "Winning" Interview: "We win so radically in our underwear before our first cup of coffee, it's scary. People say it's lonely at the top, but I sure like the view," Charlie Sheen told ABC News' Andrea Canning in an interview after he made headlines for slamming the creator of "Two and a Half Men," the hit show that made Sheen the highest paid actor in television. Sheen's bizarre behavior - he insisted he had "tiger blood" among other declarations - during the interview and in the months to come stirred a media frenzy. He was later dumped from "Two and a Half Men" and replaced by Ashton Kutcher. Sheen, who has since expressed regret for his "out there" comments, is slated to appear in the FX series " Anger Management" in the summer of 2012.

4. The Amanda Knox Appeal: American exchange student Amanda Knox spent four years in an Italian prison, convicted - along with her former boyfriend, Italian native Raffaele Sollecito - of the brutal slaying of her roommate, Meredith Kercher. This year, after a dramatic appeals case in which defense lawyers sought to discredit the forensic evidence used in the original trial, both Knox and Sollecito were set free. Ivory Coast drifter Rudy Guede was convicted of Kercher's murder in 2008. At the time, prosecutors argued that Guede, Knox and Sollecito killed Kercher together.

5. Wrong Turn - The Kati Kim Story: It was supposed to be just another family road trip. But a wrong turn left the Kims  - husband James, wife Kati and their two young daughters - stranded in the Oregon wilderness during a snowstorm. Days spent enduring freezing temperatures and painful hunger left the family terrified that they wouldn't survive and led James Kim to make the ultimate sacrifice. Kati Kim told her heart-wrenching story to ABC News.

What story did you think was the most unforgettable of the year? Vote below!

What Was the Most Memorable 20/20 Story of 2011?

Public Opinion View Results