Ultimate Spider-Man
While waiting for any of Spider-Man's missions to load, hold Select to turn his red costume into Venom's black costume.
Get a 80% game completion to unlock Carnage in Multiplayer mode.
Get a 100% game completion to unlock Symbiote Spider-Man (black costume) in Multiplayer mode.
Note: This only works if there is a ceiling above Venom. While playing as Venom and he is dying (when he falls to his knees and flops over), drag the stylus from him to the ceiling. He will resurrect and you still be able to play, but with an empty life bar.
When you fight Electro, about half way through the game, hit him with your tendril. When he turns blue, use the stylus to throw blue mail boxes and the car. Note: The car will respawn if you destroy it. If he gains health, use the tendril when he is red to take out the street lights. Note: The lights will flicker after you hit them, but if they are not out he can use them to regain health.