Two answers from my experiences. For sheer numbers of AFV's killed in games, my vote would be the German 75L and American 76L, either as guns or mounted on an AFV.
For the most deadly "one shot, one kill" I would say the panzerfaust. Vaguely remember a Normandy game many years ago, Brits and Germans. IIRC the Brits had 7 or 8 tanks at at start and Germans had a couple StuGs. My wily German opponent kept my attention focused on his StuGs while his deployed infantry slowly spread out to cover his flanks. Dense bocage limited movement and it seemed every time I tried to get one of my tanks into position to hit his StuGs one or more of his halfsquads would move up behind a hedgerow and "faust" me. Those British tanks not "fausted" were KIA'd by the StuGs. End of game every British tank was KIA....both StuGs, not a scratch. Lesson learned.