To unlock jets, submarines, spacecraft , and Titan class mobile armors, locate one in versus mode, weaken it, and deliver the final blow yourself. If an ally does the final shot, you will not unlock it. Once you kill it and save, it will be available for use in versus mode. An example is the G Fighter. Mobile Suits can jump on and ride it while the other player steers. Press R2 to cut thrusters and sit there. Another example is the Byg Zam. It is a two legged ball with a lot of particle cannons and a shield that makes it invincible to beam weapons.