AAA. If he really got highscores of every single videogame in the world the same day they were published, he must have played them at least (probably earlier) since The Seventies. Note that videogames were originally only played in universities or similar places, meaning that he wasn't very young back then (unless he was just that good in school). In other words, he's over 60 and he's the best gamer in the world.
Less Than Three Comics' Uncle Sam manages to hold his own against a horde of ninjas...at around 80 years of age. Sure, Mr Perfect helped him out, but the <3-Verse's oldest superhero held his own.
Semi-retired mystery man The Stranger of Red Panda Adventures would prefer to stay retired but Nazi Germany and other magical forces won't let him.
Sensei Tetsuo Ito of the Whateley Universe is a little old (non-mutant) man, but a master of martial arts who is capable of beating the snot out of mutants in his classes, or even taking out a Syndicate battle-team.
The Greatest Freak Out Ever videos on Youtube. In one video, the always-angry older brother is whacked in the face by his grandmother!
Burt from We're Alive, as is befitting a crazy Vietnam vet who has been stocking everything from claymore mines to automatic rifles since the 60s, and kills 20 or more zombies with a single clip.
Tasakeru: The decrepit old wolf called Drake delivers a savage beatdown in the opening chapter of Book III. Said beatdown involves throwing his opponent against a very large tree at a high velocity.
An odd case is in Xionic Madness Episode 5 Part 3 where Zero the last member of the Bolverk Team (Him, Askad, Omega and Kary) states he will die within a VERY short time (regardless), charges into a ARMY of enemies in his last armor while leaving his student to finish what he and the others started.