Meat Boy
One of the funnest flash based games to ever hit newgrounds. I just hope that it can be stretched out into a full length game, as it is in the "casual" genre of gaming.
**Request: Please insert a link to your flash game so people realize this was a newgrounds game and quit whining about how it's an ad. It's an ad for a NEWGROUNDS game, which is freaking awesome! It's another example of how underdogs can still make games in the multimillion dollar gaming industry (e.g. Castle Crasher and Alien Hominid).