Have you ever noticed that GTA 3 is almost free from real shootouts?
The only missions where you have to fight on foot and actually need to use a machine gun are ,,grand theft aero'' , Liberator, Arms Shortage, triads and tribulations and the last mission.
All other missions are : drive to this place here, collect the items there, destroy the car during that time etc etc
Thats why grand theft aero is my favorite mission, finally i can use my mg16 and shoot those colombian bastards from a safe distance and i actually have some cover ( the van in the airport and the boxes in theconstruction site)
But thats it!