In Tiberian Sun, you can abuse any weapon that uses Burst logic (a weapon that fires two or more shots per round, like the Mammoth's dual cannons) to fire with no delay between shots. Select a unit with such weapon, and move it somewhere where it can fire at the enemy on its own (without you commanding it to). When the unit fires, use the stop command (default S) quickly between the shots, and repeat this process. The unit will keep shooting at the enemy as long as you keep hitting stop. The downside to this is that you can't pick any particular target yourself, and must let the unit "decide". Also, giving the unit stop command also stops it from moving, chasing a target, etc. This works best when defending, IMO.