[Conroy]

The best way for an anti cheat system in my experience is to compare client side with server side. This means limiting the player to a certain amount of weapons, and when he buys/sells/trades weapons, his/her user file is saved with the weapons he has. Then create a timer which will compare the players weapon to the information in his/her user file, if they do not match then reset weapons, if they do match then take no action.