Part 13 - Priority: Tuchanka
Part 14 - N7: Cerberus Fighter Base
Part 15 - Priority: The Citadel
Part 16 - Mesana: Distress Signal
Part 17 - Arrae: Ex-Cerberus Scientists
Part 18 - Priority: Geth Dreadnought
Part 19 - N7: Fuel Reactors
Part 20 - Rannoch: Geth Fighter Squadrons
Starting at level 59 (as high as I could get on my first playthrough). The enemies scale in difficulty with your level, so this guide is as hard as it gets.
I decided to play through as an Adept because of how dramatically different the gameplay is compared to EVERY OTHER THIRD PERSON SHOOTER. I played through Mass Effect 1 & 2 as an Infiltrator (the sniper class) and had no idea how fun the game could be if you don't play Mass Effect as a generic third person shooter.
Vanguard is also an incredibly fun class to play as, but not on Insane difficulty (or Gold for multiplayer). The Jump ability and lots of fast paced shotgun action is super fun, but you will die A LOT on the harder difficulties.
If you're playing on the PC and want to use my save file, you can download it. My Mass Effect 3 save file.
To import the save file
If you're having problems, you can find more extensive instructions and lots of other Mass Effect save files on MassEffect2Saves.com.
You will be using Throw and Warp (and Liara's Stasis) for 99% of your kills throughout this game. Energy Drain is also very helpful for survivability and quickly draining shields.
You won't be using Shockwave, Singularity, Pull, or Cluster Grenades very much (if at all), so spec those out however you like.
Use weapons that let your recharge bonus stay at 200%, which limits you to 1 light gun. I like using the Predator pistol.
Buy the blood dragon armor when you can for the Power damage and recharge bonuses.
Liara! Max out her Stasis as quickly as possible.
Use whoever you like for the second squadmate. I will be using Javik (when I can) simply for the extra Biotic detonations.
I'll be making videos for all of the main missions and 'action' sidequests, but I will be skipping ALL cutscenes and 'talking' sidequests.
Processor: Intel® CoreT i7 2700K 3.5GHz/3.9GHz Turbo 8MB L3 Cache GT2
Memory: 16GB Kingston HyperX DDR3-1600 (4x4GB)
Graphics and GPGPU Accelerator: 2x NVIDIA® GeForceT GTX 560 4GB Total GDDR5 in SLI w/PhysX
Power Supply: 850 Watt Seasonic® X-850
Hard Drive Bay One: 20GB Intel® 311 Series SSD (w/ TRIM) [SSD Caching ONLY]
Hard Drive Bay Two: 1.0TB Hitachi 7200rpm 32MB Cache SATA