OK, this one might either be a gift or a curse, depending on your viewpoint. A rare few individuals have near-perfect recall of every day of their life. Give them a date, even years in the past, and they remember in remarkable detail everything that happened to them, and sometimes even what happened in the rest of the world. A 2010 documentary called "Unforgettable" featured Brad Williams, one such person with extraordinary autobiographical recall. Before you go wishing you could relive every day of your life, though, pause and take a breath. Sure, it’d be great for those moments of bliss (like your first love or that time you got the only A on the chemistry final), but not so cool for those other days (we all know which ones) that are probably best left in the hazy past. (This photo shows Williams with the trophy for winning the Wisconsin state spelling bee in 1969.)