This is a strange thing to talk write about. But I’m going to write about it anyways.
First thing first – you will actually need to play this game often as you will need to reach certain levels in the game when you will be able to buy the cool items and the very best weapons. This will also result in some of the best weapons since you will level up and gain a lot of money. To do all of the steps that I mentioned, you will have to complete missions. There is a ton of missions available and some of them are easy to do so you won’t have much problems doing them. You can see the full list of missions here: http://www.supercheats.com/gangstar-vegas/walkthrough/mission-types
Just go trough them and you will see that you have nothing to worry about since most of them are easy to complete. Some of them will be harder to complete, but you will get a higher reward from it so it’s really good that you complete the hard ones as well. Now, the best weapons in this game are the ones that costs the most. Those will be sub-machine gun, sniper rifle and the rocket launcher. Rocket launcher is great since it deals area of effect damage and it’s really easy to destroy buildings and cars with it. You won’t have problems with the army as well since you will just shoot a few rockets and they will go away. The problem of getting these weapons is that you will spend quite the amount of money on these ones. They are tier 3 and they will cost a lot – smaller ones cost $400.000 and if you don’t do enough missions, you won’t be able to buy those weapons for your arsenal. So don’t waste your time, start going trough the missions and start saving the money for the best weapons in the game!