The best speaker you ever heard?

In my opinion, the speaker is by far the most important part of the audio system. After all, it is the only part you hear. OK, the other stuff really matters a lot, but without a great speaker... No go.

I am a bit 'speaker-obsessed' I guess, and now I am wondering: What are the best speakers you have ever heard, and what made them the best?
The best sounds I've heard recently have come from Magico Minis, the latest and greatest large Maggies (20.?), PSB Synchrony, MBL 111s and my own OHM Walshes.

Not to say these are categorically the "best", only the best sounding I have heard recently. Much of that is likely due to proper setup and matching to room and other components.
The most impressive speaker I've heard was Isaac Asimov at Rutgers in the early seventies. I loved the Foundation Trilogy.
2008 CES- Venetian. MBL 101 powered by MBL Amps.
Incredible display of brute power. You never heard Pink Floyd like this.