All missions - At the "Campaign/Bonus/Options" screen, press Down, Up, Left, Right(3), Up, Down to unlock all missions, including the two Cybertron missions. If you entered the code correctly, the screen will flash.

Cybertron missions - At the "Campaign/Bonus/Options" screen, press Right, Up(2), Down, Right, Left(2) to unlock two Cybertron missions. If you entered the code correctly, the screen will flash.

Play as Generation 1 Jazz - At the "Campaign/Bonus/Options" screen, press Left, Up, Down(2), Left, Up, Right to unlock Generation 1 Jazz. If you entered the code correctly, the screen will flash. Select the "Bonus Features" option, then choose the "Generation 1" selection to use the new appearance.

Play as Generation 1 Cartoon Megatron - At the "Campaign/Bonus/Options" screen, press Down, Left(2), Down, Right(2), Up to unlock Generation 1 Cartoon Optimus Prime. If you entered the code correctly, the screen will flash. Select the "Bonus Features" option, then choose the "Generation 1" selection to use the new appearance. Alternately, collect all the Decepticon secret icons in the Decepticon campaign.

Play as Generation 1 Cartoon Optimus Prime - At the "Campaign/Bonus/Options" screen, press Up(2), Down(2), Right(3) to unlock Generation 1 Cartoon Optimus Prime. If you entered the code correctly, the screen will flash. Select the "Bonus Features" option, then choose the "Generation 1" selection to use the new appearance. Alternately, collect all the Autobot secret icons in the Autobot campaign.

Play as Generation 1 Robo-vision Optimus Prime - At the "Campaign/Bonus/Options" screen, press Down(2), Up(2), Right(3) to unlock Generation 1 Robo-vision Optimus Prime. If you entered the code correctly, the screen will flash. Select the "Bonus Features" option, then choose the "Generation 1" selection to use the new appearance. Alternately, successfully complete the Autobot campaign.

Play as Generation 1 Starscream - At the "Campaign/Bonus/Options" screen, press Right, Down, Left(2), Down, Up(2) to unlock Generation 1 Starscream. If you entered the code correctly, the screen will flash. Select the "Bonus Features" option, then choose the "Generation 1" selection to use the new appearance.

No traffic, police, or military - At the "Campaign/Bonus/Options" screen, press Right, Left, Right, Left, Right, Left, Right. If you entered the code correctly, the screen will flash. The only vehicles remaining will be parked.

Defeating the cement truck Decepticon - When you are fighting the cement truck Decepticon as Ironhide, transform and run him over to knock him down. Then, pick him up and throw him.

Secret icon locations

Autobots
The Suburbs

1. The High School: On the roof of one of the High School buildings.

2. Bobby Bolivia's: Behind a building in the back of the used car lot.

3. The Mall: On the roof of the main building.

4. Sam’s House: Behind the billboard on the roof of building closest to Sam’s House. Drive down the street Sam's house is on towards the city. It is on the roof of the first building you approach.

5. Power Plant: On top of a fuel oil tank around the middle of the Power Plant.

More Than Meets the Eye

6. The Police Station: There is a ring of buildings around the central police station. The icon is behind middle building in this ring.

7. Power Plant: There is a park near the Power Plant. Look closely in the park to find it.

8. The Baseball Field: In the parking lot right next to the actual field.

9. The Police Station: In the alleyway of a square shaped cluster of buildings found on the street connecting the Police Station and the mall. It is on the right hand side of the street if going from the Police Station to the Mall.

10. The Baseball Field: On the roof of a building in the triangular shaped cluster of buildings between the Baseball Field and the Mall.

Inside Hoover Dam

11. Central Control Area: Inside the control room (progress through the story missions).

12. The Containment Lab: In front of Megatron (progress through the story missions).

13. Service Tunnels South C, D: In a corner to the right of the tunnel leading towards Service Tunnels South A, B area (close to the Chapter 1 dot on the mini-map, although on the opposite side of the wall).

14. Service Tunnels South C, D: Heading towards Service Tunnel North B, in a cubby hole on the left just before the road leading to the Central Core Area, above a health pick-up.

15. Service Tunnel North A: On the first level of the generator structure closest to the tunnel, on the side of the structure facing you as you come out of the tunnel.

The Last Stand

16. The Construction Site: Across the street on top of the tallest, tapering building.

17. Central Park: Near the bird statue.

18. City Boulevard West: Roof of tall, brick building near Chapter 3.

19. Central Park: Next to a water tower on top of a building across the street from the bird statue’s right wing tip.

20. Central Park: On the roof of the third cluster of buildings from Central Park directly behind the obelisk (from the starting point, go forward straight over the first two clusters of buildings. The icon is on top of the third set of buildings, a small one story building is to the right and a “Lush Dog's” billboard is to the left).

Decepticons

SOCCENT Military Base

1. U.S. Military Airbase: Next to the hangar near Chapter 1.

2. U.S. Military Airbase: Behind a building on the opposite side of the base from Chapter 1.

3. Supply Depot East: Near the tank lot (you can get it in the Attack sub-mission).

4. Bedouin Village: Near the center of the village.

5. Bedouin Village: Across the paved road from Bedouin is a cluster of small bases. The icon is next to the L-shaped base closest to the square base.

The Hunt for Sam Witwicky

6. High School: In the park next to the high school.

7. Bobby Bolivia’s: In the highway tunnel near the used car lot.

8. The Mall: In the middle of the three way alley in the cluster of buildings immediately between the Mall and the Baseball Field.

9. Housing Estate North: Between two houses on an elevated row of houses (first two house on left as you come up towards the dead end).

10. Sam’s House: Behind the brown house that is between two white houses. There is a health pick-up in front of the brown house.

A Gathering Force

11. The Tank Depot: Between two long buildings near the mountain.

12. The Recreation Area: Between two buildings on a curved part of the road (near the Baseball Field).

13. Roof of a building between the Recreation Area and the Aircraft Depot.

14. The Aircraft Depot: Behind a building that is near a fuel oil tank.

15. The Residential Quarters: In the middle of the larger housing circle.