Rav Shmuel Mohilever זצ"ל
Rav Yitzhok Elchonon Spector זצ"ל
In an absolutely brilliant piece, on the inimitable Seforim blog, Rabbi Chaim Rappoport of London exposes the efforts to bowdlerize R. Shlomo Zalman's Auerbach זצ"ל's book on Shmittah, because he validates the Heter Mekhira (without, himself, endorsing it). As it turns out, the group of Gedole Torah who either endorsed or acnowledged the validity of the Heter Mekhira included a galaxy that make you shake when you invoke their names.
I hope that this won't be taken as grandstanding, but here they are:
Rav Avraham Yitzhak ha-Kohen Kook זצ"ל
R. Isser Y. Unterman זצ"ל
Rav Tzvi Pesach Frank זצ"ל Rav Isser Zalman Meltzer זצ"ל
Rav Shaul Yisrael זצ"ל