Well this is not really "unlimited" but when you run out of guns, you just go onto your GTA phone and apply the code!
Unlimited Health (basically):
1. Slide up your phone on GTA 4
2. Go to the typing pad by pressing "up" while still on the first screen of ur phone.
3. Enter this code on the keypad and then call: 3625550100
4. It will say something about "cleaned the mean streets" and that just means you did it right...
5. So, from now on, on the first screen of ur phone, there will be a Cheats section. And when you go there, all the cheats you have entered will be in a list, and so, once you run out of health, go to ur phone, cheats, and press, "Full Health" and ur health will become full again!
Unlimited guns (basically):
1. Slide up your phone on GTA 4
2. Go to the typing pad by pressing "up" while still on the first screen of ur phone.
3. Enter each of these codes on the keypad at a time, and then call:4865550100, and then 4865550150.
4. It will say "Weapons Tier One" for the first code and "Weapons Tier Two" for the second one.
5. So if you ever run out of your shotgun, or your RPG, then just go to cheats, on ur phones first screen, find the gun cheats, and press both of them!
UR DONE!