Pause game play, select Extras, then enter one of the codes.

Avenging Cycle   - 5T3CQU
Beetle           - KXFQ87
Black Cat        - P9OWL0
Captain America  - 7HWU4L
Carnage          - AA0Z50
Classic Thor     - H8CSE6
Howard the Duck  - J58RSS
Hydra Soldier    - B7AA3K
Iron Man Mark 17 - 2NGSRZ
Iron Man Mark 38 - CK7SDS
Iron Patriot     - Q5X1J5
MODOK            - SZ8Q06
Pumkin Chopper   - 35E41W
Pumkin Chopper   - 35E41W
SHIELD Staff Car - D5B7O3
Spider Bike      - SH9MZQ
Spider-Man       - WFOZXQ
Studs x2         - UZFBG4
Thor 2014        - H8CSE6
War Machine      - TQ4C57
Wolverine        - OAW2LB