Perpendicular Banshee fire
From Halopedia, the Halo wiki
90 Degree Banshee Fire
This is a neat little trick. On the level "Two Betrayals" when you hop into the Banshee fly back into the control room. Nose-dive into the large pit until you hit the bottom. Then get the Banshee to look directly up, when you start flying upward your fire should go to the side. When you get out of the pit however it will stop and will fire normally.
