As the decade draws to a close, we're going to hear a lot of debate about the fight of the decade and the fighter of the decade and so on. But I think the above video can pretty well end any debate about which fighter this decade made the best face after getting knocked out. That would be Hiromasa Masuda, after being KO'd by Haruaki Otsuki in March of 2002.
As this article about Otsuki explains, Otsuki and Masuda were meeting in the first match of an eight-man tournament. Masuda was favored, but 53 seconds into the first round, Otsuki used a punch-head kick combination to knock Masuda out and leave him looking like something out of a bad movie. Fortunately, Matsuda was OK.
Otsuki was hurt, though, and the foot injury he suffered on the kick prevented him from advancing to the second round of the tournament.
Thanks to Jordan Breen on Twitter for the heads-up on this one.