A good friend of mine played an all-in grappler with retardism (literally a caveman) in a campaign that I ran. It sparked so many ridiculous moments that I still smile fondly remembering it years later. A favorite was still him trying a jump check to leap from their moving aircraft that was in the middle of a dogfight to try and tackle the enemy aircraft all because he was too stupid to understand physics, and then he rolls a nat 20 on the check, passes the grab check to get hold of the other craft once he's there, and then proceeds to rip the door off, go inside, and beat the enemy crew to death.