Unlock the following Avatar Awards by performing the corresponding tasks:

AVATAR AWARD - HOW TO UNLOCK
Male/Female GAC helmet - Unlock the "Boom!" achievement by getting 30 headshots in any level, under the Officer or better difficulty setting.
Male/Female GAC armor - Unlock the "Best Cop This City's Ever Had" achievement by completing the game under the Officer difficulty setting.
Male/Female Logo shirt - Unlock the "Protect The Innocent" achievement. When you reach the television studio, enter slow motion and kill the two guards; all four hostages must survive.
Male/Female GCPD shirt - Unlock the "Brawler" achievement by completing any level excluding the Prologue without firing a shot.
Male/Female Jack and Shadow shirt - Unlock the "Finish Him Shadow!" achievement by combining Jack and Shadow to kill 20 enemies in any level, under the Officer or better difficulty setting.

Complete the game under the Detective difficulty setting to unlock the GAC soldier gamer pic.

ACHIEVEMENT - HOW TO UNLOCK
Just like Dad would have done (15 points) - Complete the game on any difficulty level.
Best cop this city's ever had (25 points) - Complete the game on Officer difficulty.
Retribution (50 points) - Complete the game on Detective difficulty.
Crossing the line (15 points) - Defeat the Enforcer with a Takedown.
Shown the ropes (15 points) - Complete the fight with Frank..
Shad-owned (10 points) - Perform a silent kill with Shadow.
Smile, you son of a… (10 points) - Take out a GAC Tank.
That's what you gets! (10 points) - Kill an enemy by knocking or throwing him off a ledge.
Got your GAC (10 points) - Take a GAC hostage.
Get ready for a surprise! (10 points) - Leap over and kick an enemy from cover.
Brawler (50 points) - Complete any level (excluding the Prologue) without firing a shot.
Crime and punishment (15 points) - Perform 50 takedowns.
Dog’s dinner (15 points) - Perform 50 Shadow kills.
Bring a gun to a fist fight (15 points) - Perform 50 disarms.
It’s all in the timing (15 points) - Perform 50 counters.
Featherweight (10 points) - Perform 200 3-hit combos.
Heavyweight (20 points) - Perform 100 5-hit combos.
Shadowboxing (10 points) - Dash evade 50 strikes.
Dog tag (10 points) - Perform a tag team kill with Shadow.
Head banger (10 points) - Open 10 doors with a hostage head.
The price of justice (10 points) - Collect 25 cop badges.
Honor the dead (30 points) - Collect 50 cop badges.
Scrotality (10 points) - Perform a Shadow groin takedown.
Medal of merit (25 points) - Bronze rating on every level.
Medal of bravery (50 points) - Silver rating on every level.
Medal of valor (100 points) - Gold rating on every level.
Shhhhh (25 points) - Complete any level with 10 silent kills, on Officer or greater difficulty.
Perfect balance (30 points) - Achieve maximum Variation Bonus on any level (excluding the Prologue).
Boom! (25 points) - Get 30 headshots in any level, on Officer or greater difficulty.
Got your back (30 points) - Complete a level without Jack or Shadow dying (levels 3-10).
First at the scene (30 points) - Achieve maximum Clear Time Bonus on any level (excluding the Prologue).
Finish him Shadow! (25 points) - Combine Jack and Shadow to kill 20 enemies in any level, on Officer or greater difficulty. 
Once Bitten (15 points) - Clear a path for Jack.
Protect the innocent (15 points) - Save the hostages.
Shadow...keys (15 points) - Help Jack and Frank into Milton.
Man's best friend (15 points) - Acquire Shadow.
Commuter disruption (15 points) - Cause the train crash.
Guard dog (15 points) - Drag Jack out of harm's way.
Apparently I CAN kill you (15 points) - Defeat Tseng.
Fetch! (15 points) - Find a way to get Jack through the gate.
The battle, not the war (15 points) - Escape from the GAC.
Canine fodder (15 points) - Shut down the electric fences.
Air traffic control (15 points) - Destroy the choppers.
Just gimme the bottle (15 points) - Get Jack to the bar in one piece.
Keeping Faith (15 points) - Rescue Faith.
GAC hawk down (15 points) - Take out the Gunship.
Throw away the key (15 points) - Imprison Temple.
Run out of town (15 points) - Repel the GAC.
Dog of war (15 points) - Retrieve the security keycard for Jack.
Doing it the ol' fashioned way (15 points) - Defeat Redwater.
Didn't I kill you already? (25 points) - Defeat Redwater in Riot Control.

"GAC Pack" achievements
ACHIEVEMENT - HOW TO UNLOCK
You hear that? We're official… (10 points) - Complete Assault on the 87th Precinct.
Above and beyond (30 points) - Achieve Gold Rating in Assault on the 87th Precinct.
GAC in time for dinner (20 points) - Achieve maximum Clear Time Bonus in Assault on the 87th Precinct.
Contender (25 points) - Get 350,000 points in a single play session of Riot Control.
Dedication to the cause (40 points) - Get 5,000,000 points total over multiple play sessions of Riot Control.
Marking your territory (5 points) - Upload a Riot Control score to the leaderboard.
Hot head (40 points) - Score 500,000 points in Retribution Mode over multiple play sessions of Riot Control.
Retribution Master (40 points) - Score 250,000 points from Retribution Bonus over multiple play sessions of Riot Control.
Jack Slate of all trades (15 points) - Get 15 unique awards in one round in Riot Control.