Some code resources for old games are drying up. I thought this would be a nice spot. To exchange useful codes and personal tricks for older games.

QA: Anyone have any codes for any Warhammer games?

QB: What are the best tricks for SMB 3?

my favorite code is for super mario bros. when your on the game over screen holding in up and pressing start brings you back to the world you died in.

and for mario three getting the two warp whistles in world one were my favorite tricks that way you never needed the third whistle.

The main one I still remember is for the first Sonic game. Up, Down, Left, Right, A, B, Start. Can go to any level you want if you do it right.