Definately a "best of newgrounds" game
There's really not much to say. It's a fantastic game, and encompasses everything about newgrounds I love. It's weird, has fantastic gameplay, and lots of replayability. I would be surprised if this doesn't become a XBox live arcade game down the road along with meatboy.
Suggestions? Perhaps making the game longer. The final boss battle without the 1/2 damage shell reminds me a lot of Ninja Gaiden. It's super difficult, however if your skilled enough you can beat it. I nearly beat the boss at least 15X before I gave up and got the shell.
I mean... metroid slugs?! That's a new one....