Mass Effect 3 - Priority: Rannoch

You'll have to fight your way through a bunch of Geth Troopers to get to the building proper. When you get there, the front door will slam shut. Eliminate the Geth resistance and then climb the pipes to the right of the door. Make your way to the top. At the top, you'll immediately be attacked so take cover. It's important that you watch for the elevated enemies at the end of your walk way because they'll still be able to hit you. Kill them first and then deal with the enemies across the gap. Go up the ladder and turn right. At the end of this walkway, past the ladder, will be Kassa Fabrication Gauntlets. Go up the nearby ladder.

At the top, climb the pipes and you'll be on a catwalk. Below you will be some Geth who will attack. You'll have an easy height advantage so take them out. Just watch out for the numerous rockets. Once you've gotten rid of them, hop down and make your way to the end of the platform. Take a right and go inside the building. You'll come out quickly and face a lone Geth Trooper. Kill the Trooper and move to the left side. At the bottom of the ramp will be an SMG Ultralight Material.

Go down the right side ramp this time and take cover behind the giant table looking thing. You can kill all the Geth safely from here. Do so and collect the Assault Rifle Stability Dampner to the right of the table. Now go past where the Geth were. You'll make your way along a bridge and there will be enemy Geth to your left attacking from another bridge. Take them out and continue along to a point where the bridge comes to a wall. You will find the Geth Plasma Shotgun here. Next to that will be Data you can salvage.

Go through the next door and salvage more Data next to a Med Kit. When you get outside, you'll be attacked by a few Geth scattered around the area. Clear them out and activate the Control Console. When you activate it, you'll be attacked by a bunch more Geth. Immediately take cover and start using Overload and Sabotage as frequently as you can. There are lots of Rocket Troopers and even a Pyro or two to keep your eyes open for. Once they are dead, Legion/Geth VI will direct you to a door that you need to open manually.

When you activate the console to open the door, you will be attacked by a Geth Prime and two Troopers. Sabotage the Geth Prime and he'll kill the Troopers. Then just unload on him and use the extra space to run away when he gets too close. Take the elevator that he came down to the top.

The top of the lift will be a nightmare. For this single battle, you need Tali. Use your Medi-gel to revive her any time that she's down. You will have to fight three Geth Primes at the same time. There's a decent amount of room to run around in. Use the Geth Spitfire at the top to help you with them if you like. Otherwise, make very liberal use of Sabotage and keep moving. There's not really any easy way to do this. Just remember to move, sabotage, focus fire, and change weapons as appropriate and you'll probably do ok. Ohhh, and watch out for all the combat drones.

When it is dead, go to the end of the long walkway and fire your nifty targeting laser through the blue ring and into the pit. Once you've fired, hop on the escape vehicle. Take some pot shots at the Reaper and then when you dismount, it's time for some good fighting. Aim the targeting laser at the Reaper. The first hit will knock it silly and reveal a weak point. At this point it becomes a little trickier. You will have to mark the Reaper in small bursts while dodging it's laser in between. When it begins to charge it's laser, roll left and then roll right twice and it will miss every time. As soon as you finish your roll, start targeting with the laser. Don't move and the laser will charge faster. You should only have to do this twice per bombardment and after a few hits, you'll have to target the reaper one more time during slow motion. Just hold the laser on it to kill him.