There can be... only one....... Pentax- F 1.7x AFA which i manged to get my sweaty hands on just last week
I took this on Sunday with DA 55-300 and AFA 1.7x, wide open (f8), handheld at (almost) 500mm. Subject was around 200meters away. (Generally this is not a recommended combination, but in the absence of a 300/4, what the hey)
Very bright condtions around EV15 and used autofocus on the AFA which is very short quick.
If the light wasnt so good the AF would be very hit & miss, like my skills of compostion
I found the image is often affected by heat haze many times worse than optical defects. I have a shot of a superyacht from 4000m and it looks horrible, even across water. In this case the shorter distance and the 20kts of breeze help to neutralise this.