Get on a high building, equip a throwing weapon such as molotovs or grenades, and jump up in the air. When you reach the highest point of your jump, start throwing the grenades/molotovs. You will actually be flying now because you cannot throw things when in the air -- the jump will start over and remain at the same height as the building you started from. To get down again, just stop shooting. Use this trick when army, police, SWAT, or special agents are after you; they will not see you when in the air. Tanks can see you but cannot touch you.