I actually have one of those nintenod Screwdrivers to open up the cartridges and clean the insides and such. On my Quest 64 game, there's this black ink mark on it. I thought Magic Eraser would do good.. here's a pic:
Now that you mentioned it, It kinda does look a little roasted. But it DESERVES IT FOR THE TERRIBLE GAME IT IS!!! :p BWAHAHAHA!! But still, good or bad, i try to keep the games in the best condition possible.