Well, then.
Seems I have a name for the two lenses I lovingly call my 'tubes-o-doom'.
I have a Quantaray 400mm f/6.3 and a Quantaray 500mm f/8. Big, clunky, 'Oh, you actually thought your sensor was clean, did ya?' monstrosities, but they actually work well with an old 2X teleconverter I have and can pull off a decent shot provided I only use them around high noon.
500mm + 2x teleconverter from about 30 feet away out my window. This is the best shot I've pulled from either of these lenses, ever.
400mm + the (now discarded) 2X teleconverter the lenses came with. That TC was fungus-riddled, so went bye bye once I realized it.
In this shot, the two lenses are the beasts in the back. They're incredibly lightweight due to their simplistic design, which means they're actually kind of portable. The fact that they're so unwieldy due to the size (you really need a third arm to operate the things properly) means I rarely use them though. This thread has inspired me to keep an eye out on something smaller though, the IQ of these shots in this thread are amazing!