Dispersion, narrow, controlled, or bi?

I’ve been thinking a little bit about fads and trends more along the lines of basic speaker operating principles than anything else... in particular a technical discussion at DIYaudio about cardioid speakers kind of got me thinking, the most known of which are the Kinki, ahem, Kii speakers.  That got me thinking less about the moving membranes or cabinetry and much more about the radiating geometry.  

For instance: 

• Line arrays
• Open baffle 
  • Genesis qualified as both in some ways
• Electrostatic
  • Which are arguably some of the most famous open baffle speakers! 
• Horns
• Omnidirectional (Ohm Walsh)
• Partially di or bi polar
  • Speakers with rear radiating drivers
  • Bose 901s were direct/reflecting
  • Snell A speakers had at least a rear tweeter
• Coaxial
  • Some are open baffle woofers with horn tweets

So, keeping it all to radiating patterns, what is your take?  What have you heard or own that really has done you in?