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, effectively 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.

Get a fire truck:

Blow up a car using the bazooka. Wait until a fire truck appears, then car jack
it.

Taxi job:

Get a taxi, then park on the side of the road and wait. Sooner or later someone
will enter the taxi and you will earn money.

Fly:

Have molotov cocktails or grenades as your weapon. Jump in the air and quickly
and repeatedly press R2 (fire). This will enable you to fly. You may have to
do this off of the ramps and other objects. You cannot die no matter how high
you are, but keep pressing R2 while descending.

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, and 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