That depends on which "Fatman" you're looking for, as it's a popular name in games and movies. Could you clarify if you mean:
: The iconic mini-nuke launcher from the Fallout series (Fallout 3, 4, or 76)? Fatman
: The 2020 action film Fatman starring Mel Gibson as a rowdy Santa Claus? That depends on which "Fatman" you're looking for,