Use these player names for the desired effect

ITSALLUP                Level Select
LIVELONG                Unlimited Energy
NAVARONE                All Weapons
HIGHFIVE                5x Multiplier
BIGSCORE                10 Million Points
NOFRILLS                Debug
LOSEFEDS                No Cops
DESIRES                 Get Maximum Wanted Level
MUCHCASH                More Money
WUGGLES                 Display coordinates
IGNITION                Turbo Charge

Hints:

     Press Up when driving a car that has a radio to change stations.

     Go  to  the  territory  of what ever gang you are working for and
they will shoot the cops for you.

     Weapon pickups regenerate. If you're not under a time limit, hang
out until a weapon respawns, then pick it up for more ammo.

     Collect the little GTA2 logos to unlock bonus missions.

     Be  on  the lookout for ramps. To see where the ramps lead, get a
good  head  start  to build up some speed. They almost always send you
somewhere that has a special bonus.

     The cops can be your friend, especially when you're in rival gang
territory  and you need some additional firepower. Make sure there's a
cop around when the gang attacks you. As long as you don't shoot back,
the police will attack the rival gang, effectiv ely providing you with
cover.

No army on the first level:
     The  army is not available on the first level. No matter how much
you  kill  and  destroy your neighborhood, they will not show up until
you  reach level 2. The same is true for the CIA, however regular city
police and SWAT appear.

Die while invincible:
     Be  careful, you can still die when invincible by being inside an
exploding  car. The other armed men can also blow up your vehicle. You
can also die by jumping from a high location or by drowning.

Guided tour:
     Go  to the phone at the beginning of the first level. A "Schmidt"
car  will  appear  below.  Enter  it  and wait for instructions. After
finishing  the  tour,  a machine gun and a GTA2 sign will appear below
the church.

Drive the Tank:
     In  the  first level there are 3 arrows go left not following the
arrows  but get in the middle of the town. Go left and when you are at
the end you should see a building with a tank. To get on it, go around
the  building  and up the ramp\steps. Then jump, an d get in the tank.
It is a killing frenzy. You can run over cars and trucks. What I do is
point  the cannon backwords so i can shoot cars trying to get me. When
the  frenzy is over DON'T GET OUT OF THE TANK! If you do you can't get
back in.