http://www.konjak.org/section.php?section=chalkCheck out this game where you take the role of cute chalk-girl "Line" as you draw your way through 6 challenging but very fun levels where you fight polygons, spaceships, and bosses with the power of chalk.
This game is great, the controls are responsive, the music is engrossing and awesome in it's own way (VALKYRIE SCREAM!), and it never fails to keep itself interesting. The only things you could really complain about is that the action gets VERY hectic, and is mentally demanding. You can't have even the slightest of distractions if you want to survive, but the game is very forgiving anyway, so it's alright.
My only REAL complaint is that at the end of every level, the game grades your performance, from D to A, like you're in school again. This is something I dislike in every game it appears in, but I especially dislike it here. My reasoning here is that the game is short, and fun, but it's not something that would warrant repeated playthroughs, so when playing through the first time, and figuring out all the cute, gimmicks that you need to finish the level, the game sours your sense of achievement with a big, fat "D" to make sure that, even though you won, you still suck.
I'd recommend that everyone give it atleast one playthrough, it's surreal, unique, polished, and it definitely deserves your attention.
EDIT: Sonerohi points out a laughable contradiction, that is fixed now.