Stanislav Petrov, a little-known Russian whose decision averted a potential nuclear war [1].
[1] https://www.armscontrol.org/act/2017-10/news-briefs/man-save...
[1] https://www.armscontrol.org/act/2017-10/news-briefs/man-save...
EDIT: Oh, he has died. I hope people were taking him gifts.