Absolute favourite shotgun is the assault shotgun in GTA5. Best way to clear out rooms during missions and heists (Humane labs is a blast with one of those)
They are definite fun to use but they often have slow reload and are impossible to use on a controller ( although not an issue for PC gamers ) . i like that you can swap arrow type.
i like rapid fire sub machine pistols or sub machine guns. I think one of my favourite guns is The Killing floor, Schneidzekk medic gun which is basically KRISS Vector with Medic healing capabilities as alternate fire
In the case of Borderlands there is nothing I love more than a good revolver, get one with decent accuracy and damage, it'll be better than a sniper rifle, get a Jakobs where you fire as fast as you can click, it'll be better than a machine gun
Shotguns. Remember the M26 Glitch in Battlefield 3? 100 points damage with no drop off over distance and zero recoil/bullet deviation. It was the ultimate shotgun. However, before that best one was pre-nerfed USAS-12 w/ Frag Rounds. It was the ultimate sardines massacre weapon in Metro, but don't take my word for it, go watch videos of it close to release year maybe.