Compared a couple of TC's with the Sunagor 100-200mm TN yesterday. Used my big Vivitar TC for Pentax 6x7 medium format which I really like and it gives the least amount of mag out of the 3. There's a thread on that medium format TC here http://www.birdforum.net/showthread.php?t=302899
Second photo is Sunagor and last photo is the Vivitar macro focusing TC. Macro TC is 7 elements and the Vivitar medium format is 6 element and both give slightly more depth of focus than the TN I noticed. The medium format one is available as a Teleplus just as the macro focusing ones are. Rokunar also had one the same copy as Vivitar/Teleplus 6x7. Komura made a similar one too.
As well as Pentax 6x7 there was Mamiya 645 medium format and Hasselblad of course. All these TC's crop up in those mounts too.