Zipp or the Delta Pro are two great ones… so long as stopping isn’t a priority.
If you’re talking about the Zipp brake that came with the Zipp 2001 and 3001 frames, I have to strenuously object. That brake was terrible for a number of reasons, including stopping power, weight, wrenchability and not to mention that big carbon fairing that would crack on your first ride with the brake.
I have some photos of that Zipp brake in this photo album, it really is a POS:
http://s42.photobucket.com/albums/e344/refthimos/Zipp2001/
You’ll see in that photo album that I also had a Modolo Kronos brakeset. I’ve also owned the MRC aero brake, Deltas, Mavic SSC, and lots of others. Here’s my votes:
Coolest/Most Aero: Modolo Kronos. Unless you have seen one in person, you’ll have a hard time imagining just how tiny these things are. Of course, they won’t stop you for sh!t.
Most Aero (Real Usage): Omega. Have these on the P3C. Really, really nice brake and they actually work!
Best Road/Sidepull Brake: SRAM Red Aerolink. I like how these brakes work really, really well with wider rims like the Smart Enves.
Worst Brake: Zipp. Heavy, sucky… but their frames were/are awesome and definitely were way ahead of their time.