For me they are in no real order.
Shotgun in Bulletstorm. Just melts enemies and a nice big boom
Combat Shotgun in Rage 2. Not a great game but the shooting is excellent. Combat shotgun has a nice weight and feel to it.
Wolfenstien the New Order. It's dual-wielding semi auto shotguns!
Turok on N64. It seems quaint now but to me at the time it felt like the only game that rivaled Doom 2 shotgun. Enemies go flying and you see the stream of blood.
Doom Eternal Super Shotgun. Powerful as all hell..erm more powerful than hell. The meat hook for grappling enemies and you can chain it.
Funny how 3 I mentioned under the same publisher but those guys know gunplay well.