Metal Arms: Glitch in the System Cheats (GameCube)

When you play the level "Mogul Schmogul", reload at the beginning. 
  This gives you five more shots. Also, press the secondary fire button 
  to swing Mogul's club. This kills the "oil thirsty monsters" in one 
  hit, and everything else but a vehicle or turret, too.

  

Grunts with shields: The easiest way to defeat these like 
buggers, is to use coring charges with a slingshot and just fling away. 
After a few or couple of direct blasts, its shields should get 
destroyed, leaving it's weak chassis vulnerable. 

Troopers: These are usually the hardest to hit, but if you have 
the correct firepower and accuracy, you can take them out quickly. If 
you want the quickest kill, use a level 3 scatter blaster, get close 
enough, and blast it to metal shards. If your accurate enough, use the 
level 3 rivet gun and a single clip should blast them out of the sky.

Predators: These can be a real pain if you dont aim for the 
correct spots. With a rivet gun, barrage cannon(level 3 rocket 
launcher), or a stationary machinegun, aim for all four arms first. They 
are easy to disable or destroy, and once you take out all 4 arms, its 
completely defenseless.

Titans(no shield): with an accurate machinegun, or a level 2 or 3 
rocket launcher, these go down easily with shots to the torso or head. 
If your too weak and desperate for a quick kill, use one full cleaner.

Titans (shielded): If you have a nice supply of EMP grenades, 
lobe one of these covertly with a slingshot to first disable it, then 
use a level 3 rocket launcher and just blast away before it wakes up 
again. For a quick kill, use 2 cleaners, and a couple rockets if its 
still alive.

Mortars: These can take a pretty good toll on your health if you 
cant find them quick enough. Once spotted, use a level 2 or 3 rivet gun, 
and 2 full clips should be enough to take them out of commision.

 

Setrys: Destroy these without them seeing you can really save you 
from its deadly barrage of bullets and rockets. Use a level 3 rivet gun, 
empty 2 full clips, or use a level 3 barrage cannon to finish them 
swiftly.

Tips for the Zobiebotking!

First you need to make sure he is not moving. So hit him with a lot of 
shots till he stops and just sits there. Now take action and throw a 
corring charge into his open mouth! It will explode and he will start 
moving again. Do this a few more times but watch out for his evil 
minions that come out when he gets hit a few time.1 of them comes out at 
first then on the second to last time you throw a grenade in his mouth 2 
of them will show up. do this till he dies!

When playing multiplayer, if you destroy enough enemies without getting 
destroyed yourself you get a message saying "Brawling Bot Supreme". It 
would be the second message you would receive not the first. If that 
message shows up you will receive 3 robots that will help you defeat the 
enemy. The message will show up after killing 6 enemy bots without 
getting killed. This code only works if you play another person not the 
CPU.

The enemy can kill their own men, by moving around, you might get lucky 
and let them take themselves out!

Get all secret chips in the game which also 
includes getting the speed chips.  You have to collect a total of 
110 secret chips to earn corrosive city in multiplayer and you can't use 
corrosive if you have vehicles to operate corrosive use the are jumps to 
get to the top of the scaffolding where the statue of corrosive would be 
and you'll find a console activate the console to materialize corrosive 
and control him.

Start a multiplayer game with just recruiter grenades as your secondary 
weapon.  It doesn't matter whether you are playing alone.  Go to a level 
with multiple mils, have them be off when not recruited.  Recruit two or 
more, and hide behind one as you pop off a couple of shot at the other 
one.  The one you fired on will fire at you, and thus hit the mil you 
are hiding behind.  They will fight each other and not hit you, while u 
just stand there laughing.  This is best done on the level Tanks a Lot, 
with 3 mil Titans.

Finish Story Mode one time