Gantz Cheats

Unlock Ending #4
Be kind with Kishimoto. Take here in your team as much as you can and act like a leader when talking to others. At the end of the game you'll be rewarded with Ending #4 featuring Kei and Kishimoto dating each other.
Submitted by: Hunter

Unlock Gantz Bike in Story Mode
To play with the Gantz bike in story mode, you need to get a 100 points. Once you did that you will be returned to the Gantz Room. There will be a screen with 3 choices. Choose the one in the center and you'll be rewarded with the Gantz Bike. Load the clear save file you obtained and the Gantz Bike will appear in the accessories at the begining of a mission.
Submitted by: Hunter

Neko Mimi Alien Mode
Beat the game with any character other then Kurono Kei. The Neko Mimi Alien mode will be found under the Extra Option Menu.

Play as other characters
After beating the game once, go to extra option and select the first option. You'll get to choose a character to play as. You can also choose between weapons, battle items and partners.