Contra is arguably the hardest video game ever.  It takes amazing thumb skills mixed with insane memorization to map all the levels and avoid the swarm of tiny dots that can kill you.  The Konami code actually first appeared in Gradius but Contra made it famous.  Kazuhisa Hashimoto created the code for Gradius when he found the game was too challenging to play in one sit through.  He ended up leaving the code in the final release of the game.  In Contra, the code gave you 30 lives, making the game less insulting to the average player (and some advanced gamers still needed to rely on it).  Konami ended up including the same code in dozens of games.