What Was the Best Cold Opening on a TV Show?

Most cold openings for TV shows are fairly routine: introduce main plot points, add a teaser and then fade to opening credits and commercial. Every so often, though, we encounter a cold opening that so rivets our attention that we know we're in store for something special.

Case in point, one of my favorites: The Star Trek: TNG episode, "Yesterday's Enterprise," when the bridge suddenly and inexplicably changes, revealing that Tasha Yar—the ship's security officer and present-day Walking Dead grill master—never died.

I could list some others, but we want to hear from you. What are some of your all-time favorite cold openings? Please include pictures, video and links!