here's one you guys didn't think of:
A flintlock!
you have to hold it steady until the burning powder travels inside the gun and sets off the main charge, kinda hard when you're getting a face full of smoke and maybe a few sparks.
With ererything else being equal, the more energy used, the higher the kick. Recoil is all about force being aplied to move a projectile. Moving a heavier projectile the same speed takes more energy and produces more recoil. Moving a projectile faster requires more energy. Yes, it seems obvious. Other factors come into play also though. Autos and semi autos typically produce less recoil due to the guns cycling action. Muzzle breaks and boss systems can also be employed to reduce recoil.
Rimfire rifles (.22s) typically produce the least amount of recoil. Then small caliber centerfire rifles and small shotguns. After that, maybe the larger shotguns and high caliber rifles followed by magnum shotguns and magnum high powered rifles. Again, there are more variables than just size. I have a pump 12 guage 3 1/2" mag that will knock your shoulder out of joint after a box of shells, but I can shoot the same rounds all day long out of a gas operated semi auto I have with little notice of recoil.