Most “disappeared” speakers.

i had a pair of crappy advent legacys get stolen from the garage rig.. those are so diasappeared i cannot hear them anymore

+1 to @douglas_schroeder  's posts.

Whichever one I want.

....the effect of sensing the speakers have "disappeared" happens when they are setup properly

Almost any speaker can be made to 'disappear' ... this is also about your system (not solely the speaker).

I haven't heard these in a while, but I have a soft spot for wide-baffle speakers. 

The Sonus Faber Stradivari are excellent examples. While small 2-ways often disappear if properly designed and out in the room, the wide baffle speakers have their own benefits and ease of integration, and are much more location friendly. Plus, I think they're gorgeous.

Vandersteen 2Ce Sig disappears about as well as any $peaker, even with the lights on and the signal in one channel.

Costco sells this thing you plug into the outlet. Then you plug your lamp into the thing. When you press the remote the light goes out. Speakers, everything, whole system disappears.