Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
Cobra Missile Launcher (more in Veteran/Spectre packs)
Thermal Clip Pack (more in Veteran/Spectre packs)
Ops Survival Pack (more in Veteran/Spectre packs)
Medi-Gel (more in Veteran/Spectre packs)
Ammo Bonus Items (Level 1 in Recruit/Level 2 in Veteran/Level 3 in Spectre)
Weapon Bonus Items (Level 1 in Recruit/Level 2 in Veteran/Level 3 in Spectre)
Armor Bonus Items (Level 1 in Recruit/Level 2 in Veteran/Level 3 in Spectre)
Common Items (Blue)
Pistol High-Caliber Barrel
Assault Rifle Percision Scope
Assault Rifle Magazine Upgrade
Sniper Rifle Spare Thermal Clip
Shotgun Smart Choke
Shotgun High Caliber Barrel
Shotgun Blade Attachment
Uncommon Items (Silver)
SMG Ultralight Materials
Pistol Piercing Mod
Assault Rifle Stability Damper
Sniper Rifle Extended Barrel
Sniper Rifle Enhanced Scope
Shotgun Shredder Mod
Rare Items (Gold)
Consumable Item Capacity Increases
Geth Pulse Rifle
Geth Pulse Shotgun
Graal Spike Thrower
Collector Assault Rifle* (code required)
Asari Adept - Krogan Soldier
Ultra Rare Items (Black/N7)
If you discover a medi-gel container while you are already carrying as many as you can, you'll instead receive experience points that correspond to the difficulty setting on which you are playing. If you quickly bump up your difficulty setting before you open the container, you can receive a significant experience boost. Then you can change the setting again and resume normal play.
Prejek Paddlefish Intel Bonus
If you import a save from Mass Effect 2 with a live Prejek Paddlefish, take care of it carefully! Keep it alive through an entire Mass Effect 3 playthrough AND a Mass Effect 3 New Game+ playthrough you can get a special Intel Bonus from Liara's Quarters on the Normandy. The Prejek Paddlefish Bonus gives you a 10% bonus to either Weapon Damage or Power Damage.
Imported Character Bonuses
Here are the bonuses you can get from importing a Mass Effect 2 save file.
Your level from Mass Effect 2 will carry over to Mass Effect 3.
Your Squad Members will also start at the same level.
You will get Squad Points to upgrade your Powers based on your imported level. If you import a Level 30 Shepard, you will have 1 point automatically placed for you in one Power, and 59 available to place at your whim.
Your Paragon/Renegade points will bump your Mass Effect 3 Reputation meter up about one quarter. Your Morality choices will be reflected.
Reckoner Knight Armor and Chakram Launcher
Power on the Kingdom of Amalur: Reckoning demo to unlock the Reckoner Knight Armor and a Chakram Launcher weapon in Mass Effect 3. The armor "will maximize damage done in close-quarters combat while a beefed-up power cell feeds energy into weapon systems to increase projectile velocity," and that the launcher "uses a fabricator to manufacture lightweight, explosive ammunition discs."
A Personal Touch - Modify a weapon.
Almost There - Reach Level 15 in multiplayer or level 50 in single-player
Always Prepared - Obtain two noncustomizable suits of armor.
Arbiter - Win a political standoff
Battle-Scarred - Promote a multiplayer character to the Galaxy at War or import an ME3 character.
Bringer of War - Chase down an assassin.
Bruiser - Kill 100 enemies with melee attacks.
Combined Arms - Perform any combinations of 50 biotic combos or tech bursts.
Defender - Attain the highest level of readiness in each theater of war.
Driven - Return to active duty
Enlisted - Start a character in multiplayer or customize a character in single-player.
Executioner - Defeat an old adversary.
Explorer - Complete three multiplayer matches or five N7 missions.
Eye of the Hurricane - Kill a brute while it's charging you.
Fact Finder - Discover an enemy's monstrous origin.
Focused - Evolve any of your powers to rank 6.
Giant Killer - Defeat a Harvester
Gunsmith - Upgrade any weapon to level 10.
Hard Target - Call down an orbital strike.
Hijacker - Hijack an Atlas mech.
Insanity - Finish the game on Insanity without changing difficulty after leaving Earth.
Last Witness - Extract ancient technology
Legend - Mission accomplished.
Liberator - Stop a Cerberus kidnapping
Long Service Medal - Complete Mass Effect 3 twice or once with a Mass Effect 2 import.
Lost and Found - Dispatch 10 probes to retrieve people or resources in Reaper territory.
Mail Slot - Kill 10 guardians with headshots from the front while their shields are raised.
Master and Commander - Deliver most of the Galaxy at War assets to the final conflict
Mobilizer - Bring a veteran officer aboard.
Overload Specialist - Overload the shields of 100 enemies.
Paramour - Establish or rekindle a romantic relationship.
Party Crasher - Sabotage a dreadnought.
Pathfinder - Explore a lost city.
Patriot - Make the final assault.
Peak Condition - Reach Level 20 in multiplayer or level 60 in single-player.
Problem Solver - Evacuate a scientific facility.
Pyromaniac - Set 100 enemies on fire with powers.
Recruit - Kill 250 enemies.
Saboteur - Disable a group of fighter squadrons.
Shopaholic - Visit a store in the single-player campaign.
Sky High - Lift 100 enemies off the ground with powers.
Soldier - Kill 1,000 enemies.
Tour of Duty - Finish all multiplayer maps or all N7 missions in single-player.
Tourist - Complete one multiplayer match or two N7 missions.
Tunnel Rat - Survive the swarm.
Untouchable - Escape a Reaper in the galaxy map.
Unwavering - Finish all multiplayer maps on Gold or all single-player missions on Insanity.
Veteran - Kill 5,000 enemies.
Well Connected - Send a warning across the galaxy.
World Shaker - Destroy an Atlas dropped from orbit.