Some great answers here - I sure agree the shotguns with no recoil pads are not a bit fun.
My hardest-kicking is a Winchester 70 in 416 Rem Mag. Decent if standing, just bad shooting off a bench. And then this odd one - a Winchester trapper 94 in 44 Magnum. I don't know what it is about that stock, feels like it is 1/8" wide. And the whole gun with that short barrel doesn't feel any heavier than a Ruger Super Blackhawk. That little lever gun just beats me up. A Marlin in 44 I don't even notice.