Constructive critisim
drop the spritey pixelated charecter's, i'm assuming you lifted them of megaman or something old, you can tell you used the sprites for frame by frame animation which is awsome because frame by frame animation always yealds much better results than tweens and is also much more time consuming and difficult
anyway i lost track, just convert all your sprites over to vector, also you could convert all the other images you choose to use (like the covenant hover bike thing) into vector as well. Then your guns won't look out of place on your char's, neither will anything else you choose to add. Basic shading also works really well, check out any profesional flash and you see some really simple, yet beautiful and effective shading on the edges of dark colour patches on vector graphics. Check out xombie or littlefoot for example.
Anyway dude i know i said a lot but your submission is awsome i forgot how much i loved ng's and i can't wait to fix my buggy flash so i can have a shot at adding sumissions again