PQ2

The Practical Intelligence (PQ) series on PSP is a hidden gem of puzzle goodness.  I love PQ, and PQ2 is more of the same with extra elements.  Not only that, one of the extras is a puzzle editor and online posting/downloading.  It seems everyone wants to make the hardest puzzle ever, but its still a brilliant addition.  There are also weekly challenges, special themed puzzles, and a pressure-free level selector.  If none of that excites you into buying this game, try out PQ first.