Brain Age 2--the mirror.

User Rating: 8.5 | Touhoku Daigaku Mirai Kagaku Gijutsu Kyoudou Kenkyuu Center Kawashima Ryuuta Kyouju Kanshuu: Motto Nou wo Kitaeru Otona no DS Training DS
I call this game a mirror of sorts because it reveals just what you can do when put under pressure and required to focus on something. Overall, the game really is great as a time sponge. You can always just click on your DS and do a few quick brain training games whenever you have a moment or chip away at more sudoku puzzles. Overall though, I'd say this game is reviewed rather harshly by players because it reveals just how little the brain is actually used(I personally started with a brain age of 54 or so in the first installment). I think this game definitely deserves at least a once-over, even if you just buy a used copy from a Gamestop then return it the next day for your money back.