Favorite NES themes

The NES has a plethora of games, some great, some legendary, and some so-cringe worthy that they are better off unnamed. Regardless of status, some games, even the worst, included some really awesome themes. I might be hard for others to fathom, but I would play certain games just to rock out to the music. Playing a game like Teenage Mutant Ninja Turtles (the first one) just to listen to chiptunes. 

I digress, but the point remains: the NES had some kick-ass themes. What is your favorite theme?

For me, it is hard to name just one. Mega man 2 included a sweet melody for just about every stage. Batman featured a sweet bass heavy theme, and then there are melodic classics such as the Zelda theme, especially the Link's Adventure theme. 

If I had to choose one, just one. Like as if some crazed gunman ordered me to just name one, and only one, I would go with the Contra theme. What about you?