There was a japanese indie game I played sometime back that may be like what you're talking about. It had some badass sprite work, but I can't remember the name. Really small title. Free to download. Shit I wish I could remember. I think the title started with a X, Y, or Z. One of those last letters in the alphabet.
edit:
Iwanaga! I was waaaay off, lol.
http://www.youtube.com/watch?v=NyX6RJJBaFs
This is actually quite close to what I was thinking, though the idea I had in mind would be more of a platformer.
Also Contra is another obvious reference that I've never played, lol
Now that I think about it Outland is a very good reference for me. The game I'm imagining is like Megaman meets Outland meets Super Stardust or something. Anyways thanks for the help guys, I'm going to toy around with Unity and see if I can get a basic set-up going.