Top Ten Tuners of all Time??

Too much work!!

Pioneer TX-9500 II
Pioneer TX-9800 (poorer shielding though)
Pioneer F-93 (listen for yourself and make your own mind up, it was a Recommmended Stereophile component. TIC appears to not like it because a Tuner Guru chose not to try to align it.....once.....)
Pioneer F-91 similar in some respects to the vintage H-K Citation, but in the end, a less refined version of the F-91. Listen first.

Will list next year.

Does an Onkyo T-G10 tuner in true minty condition, with box manual and remote and under 100 hours usage(actually prob below 50 even) have some decent value?

For nice, pleasant sound, Magnum made/makes great tuners. In terms of looks, nothing beats the Day Sequerra tuners with the panoramic oscilloscope display.

But, for sheer RF tuning capability, decent sound and incredible build quality, to me, the ultimate tuner is the Toshiba/Aurex ST-910.