This green, round pill imprinted with M F2 is a Famotidine 40 MG Oral Tablet, per the NIH.
Famotidine is a human prescription drug. The active pharmaceutical ingredient is famotidine and is classified as, "Histamine H2 Receptor Antagonists [MoA], Histamine-2 Receptor Antagonist [EPC]."
This pill is made by Mylan Pharmaceuticals Inc.
There are 4 other green pills that with a similar imprint: "M F2". They may be a different dosage of the same drug or a different drug entirely.