A couple of trailers I saw recently really brought home the message of a good, clear high concept. The first is for NBC's upcoming TV series Awake. Yes, after watching it, read that again, it's a network TV series. It looks absolutely fantastic and I guarantee I'll be there to watch, and I suspect once you've seen the trailer you'll be there too, the high concept is just that good.
The second is for the upcoming film Another Earth. The high concept here blows my mind as well. Both of these trailers have fantastic ideas with characters so deeply intertwined in the concept it seems almost impossible to separate them. Both concepts, when taken alone might seem a bit goofy and far-fetched, but with the character involvement they become a fantastic hook.