Be sure to always make a backup of Coalesced.ini before modifying it.

(Link) Modding out the UI in ME2

If you want to take screenshots in-game and don't have Fraps, bind some key to the "shot" command by doing the following:
Go to your Mass Effect 2 Install Dir, then >BioGame\Config\PC\Cooked
Make a backup of Coalesced.ini
Open Coalesced.ini and just add:

Bindings=( Name="F8", Command="shot" )
This will bind Screenshot to the F8 key. Feel free to use a different key if you'd like

Screenshots are stored in My Documents\BioWare\Mass Effect 2\BIOGame\Screenshots (not in Mass Effect 2\Screenshots, for some reason). Also, they're saved as .BMP.

Thanks to FronzelNeekburm for this information!

How to edit in weapons you character isn't supposed to be able to use, using gibbed's Save Editor
(Note: this won't give you access to DLC weapons you haven't purchased.)
This info brought to you by HennesyHero on the Something Awful forums
BACKUP YOUR SAVES before attempting this!

"Go into the raw tab and change both the data in your loadout and weapon's tab so that you have the correct code. I confirmed by giving myself an assault rifle I wasn't supposed to have and playing through the suicide mission to check its stability. It didn't break so this method appears to be okay.

Here are some weapon codes:
SFXGameContent_Inventory.SFXWeapon_MassCannon = Widow
SFXGameContent_Inventory.SFXWeapon_Machinegun = Revenant
SFXGameContent_Inventory.SFXWeapon_FlakGun = Claymore
SFXGameContent_Inventory.SFXWeapon_SniperRifle = Mantis
SFXGameContent_Inventory.SFXWeapon_AntiMatRifle = Viper
SFXGameContent_Inventory.SFXHeavyWeapon_GrenadeLauncher = Grenade Launcher
SFXGameContent_Inventory.SFXHeavyWeapon_MissileLauncher = Missile Launcher
SFXGameContent_Inventory.SFXHeavyWeapon_FreezeGun = Avalanche
SFXGameContent_Inventory.SFXHeavyWeapon_NukeLauncher = Cain
SFXGameContent_Inventory.SFXHeavyWeapon_ParticleBeam = Collector Particle Beam
SFXGameContent_Inventory.SFXHeavyWeapon_FlameThrower = Firestorm
SFXGameContent_Inventory.SFXWeapon_HeavyPistol = Predator
SFXGameContent_Inventory.SFXWeapon_HandCannon = Carnifex
SFXGameContent_Inventory.SFXWeapon_AutoPistol = Shuriken
SFXGameContent_Inventory.SFXWeapon_SMG = Tempest
SFXGameContentDLC_HEN_MT.SFXWeapon_TacticalMachinePistol =Locust
SFXGameContent_Inventory.SFXWeapon_AssaultRifle = Avenger
SFXGameContent_Inventory.SFXWeapon_Needler = Vindicator
SFXGameContent_Inventory.SFXWeapon_GethPulseRifle = Geth Pulse Rifle
SFXGameContent_Inventory.SFXWeapon_Shotgun = Katana
SFXGameContent_Inventory.SFXWeapon_HeavyShotgun = Scimitar
SFXGameContentDLC_Pistol.SFXWeapon_LaserPistol = Phalanx
SFXGameContentDLC_Desert.SFXWeapon_DesertAssaultRifle = Mattock
SFXGameContentDLC_CER_02.SFXWeapon_IncisorSniperRifle_CER_02 = Incisor
SFXGameContentDLC_MCR_02.SFXWeapon_GethShotgun = GPS
SFXGameContentDLC_PRE_Cerberus.SFXWeapon_CerberusShotgun = Eviscerator

If you input the code wrong, if you're lucky, it'll just default you to a basic weapon like the avenger. If you're unlucky, it'll corrupt the save. If you're really unlucky, well, Overlord. Good luck.

How to Speed Up Starting a New Game

If you'd like to start a new game without having to watching the Normandy Blowing Up & Medical Rebuilding movies, simply cut these files and place them in a new folder for safe keeping. You will still need to do the "Rescuing Joker" part where you control Shepard, but after that you should wake up at the Cerberus station.

**DO NOT DELETE THEM, JUST MOVE THEM TO A NEW FOLDER**

load_f99.bik
ME2_Opening_SunMid_ESN.bik
ME2_Opening_SunMid_INT.bik
Opening_End_Seq.bik
Opening_End_SeqFM.bik
Opening_Seq_INT.bik
ProNor_Pod2.bik
ProNor_Shepard_Rebuilt.bik
ProNorEscape.bik
ProNorEscapeAsh.bik
ProNorEscapeKaid.bik

Put these back where they came from as soon as you wake up on the Cerberus facility or else your game will crash.