Sudokuhax

Sudokuhax was the original DSiWare exploit, made for the game Sudoku by EA. It was only available through the American and European/Australian DSi Shop, for 200 Nintendo Points. The exploit works by hacking the game's savedata to make it to load the file "boot.nds" from the SD in DSi-mode. Sudoku was removed from the DSi Shop, in March Nintendo/EA patched it and it's available for download again, see the HackMii post.

More instructions and download is available here: Hackmii post