Please.
I don't really remember much, nor do I have pics, since I last played this game about a decade ago, in my pre-teen years, but please try to help the best you can.

It's obviously a run and gun like Metal Slug (X), it used 2d sprites too, and might have used 3d for certain events, such as a boss appearing. Backgrounds I remember as 2d graphics as well.
The style was gritty and cartoonish, but more anime than western animation.
At the start of the game, you had the choice between a boy or a girl.

As for levels, I recall the first one being on an oil rig/super tanker/aircraft carrier/factory etc. The first boss I remember was a 20 foot tall mecha that flew in from the background, and during combat flew around the screen. After defeating him, you went inside.

A later level was situated in some swamp environment, and you fought a kind of water-dwelling tentacle monster at one point.

An even later level was in some underground facility/lava caverns, a majority of which consisted of elevator rides/jetpack fares up a screen-wide shaft.

And that's really all I can remember. If you could help me find this, it would be greatly appreciated. If not, oh well:/

_Zexion