Okay, there's (in my opinion) a very tough mission, in which you need to fight 3 ranking ACs without a break. The first AC, you fight alone, so he's not that tough, but its on an elevator, and you start out on the bottom, while he starts on top. Get the height advantage and he'll be a pushover.

The next two are very tough, because you need to fight them together. I had a little plan of my own, tough.

Buy a Chain gun for your back weapon (for either side or both), and get into the nearest corner. The corner may not seem like such a nice place, but since one AC comes in the fight slightly later, and from the back, it can prove VERY effective. It proves effective, because the strategy for most computer ACs is to get behind you and attack.

In the corner, you can see AND attack everything.