Top of the line Grot-O-Matic Big Shoota

 The best weapon teeth can buy. Well, maybe. Ah, who are we kidding. 

Armor plate protects the ammo feed, sight is underneath the Big Shoota (and partially covered by the front armor plate on the Rhino, of course). Just needs the magnets, when I find them. Added the most useless ram spike on the Rhino ever.

Now to further detail the rest, add 2 more exhausts, and start work on the rear doors.