I searched around the internet and came up with these cheats.....
[*]Colonel rank
At the title screen, press Triangle, Square, Circle, Square, Triangle, Circle, then start a new game. This results in a game with a level 3 shield, level 3 sensor, radar, no weight limit, beginner level of all weapons, 99 clips for each, and bonus points displayed when earned.
[*]General rank
At the title screen, press L1(2), L2(2), R1(2), R2(2), then start a new game. This results in a game with a level 3 shield, level 3 sensor, radar, no weight limit, intermediate level of all weapons, 99 clips for each, and bonus points displayed when earned.
[*]Master of X-Squad rank
At the title screen, press Circle(4), Triangle, Square(4), then start a new game. This results in a game with a level 3 shield, level 3 sensor, radar, no weight limit, master level of all weapons, 99 clips for each, and bonus points displayed when earned.
Hope these help playing X-Squad alot easier :D
GOOD GAMING!!!