Oh yeah, there is a mini tank that you can control. It is in all of the levels I played, and you can drive it one way, look another, and shoot. It fires a high-energy projectile that explodes. It is cool.
I doubt it would be an actual tank shaped thing - it would just be really naf to have in the game...could it be a gadget? Perhaps "Q's Pet" that we see in AVTAK? It could be an adapted gadget like that?