I haven't gotten around to it, but surely someone must've tried it by now. If so, what'd you get from it?

From GameFAQs
 
 

Contra Stage 1 Music *new*

During the loading screen for mission one, entering the classic Konami Code will change the mission's background music to a remix of Contra's first stage! As usual, the code is Up, Up, Down, Down, Left, Right, Left, Right, B, A. This code MUST be entered before the loading of the level finishes (IE, before the Press A prompt). A voice clip of "Let's rock!" will confirm the code was entered successfully.

Says on the wiki page it plays a remix of the contra music from the first level. 

That's weak. I was hoping for more lives, so that I could, y'know, beat the game.

" Says on the wiki page it plays a remix of the contra music from the first level.  "

The one code I still remember from all the way back to may childhood was for Street Fighter 2 on the SNES. 
If you entered Down, R, Up, L, Y, B, Start at the menu you would unlock alternate colors for the fighters. Those old-school codes were so cool. I wish more games still did that nowadays.

" That's weak. I was hoping for more lives, so that I could, y'know, beat the game. "

" The one code I still remember from all the way back to may childhood was for Street Fighter 2 on the SNES. If you entered Down, R, Up, L, Y, B, Start at the menu you would unlock alternate colors for the fighters. Those old-school codes were so cool. I wish more games still did that nowadays. "

" @McGhee_the_Insomniac said:

" The one code I still remember from all the way back to may childhood was for Street Fighter 2 on the SNES. If you entered Down, R, Up, L, Y, B, Start at the menu you would unlock alternate colors for the fighters. Those old-school codes were so cool. I wish more games still did that nowadays. "

Would you like to buy them instead of unlocking them for free?  No?  Yeah me neither. "