Fifty-degree Banshee fire
From Halopedia, the Halo wiki
The 50 Degree Banshee Fire is a glitch that may only be performed in Halo: Combat Evolved or Halo: PC.
To perform that glitch, play any level with a Banshee (i.e. Assault on the Control Room or Two Betrayals). Use the Banshee and shoot at a tree when it's close to you. All your plasma will barely graze the tree and shoot upwards; so you could, in theory, take out units directly above or below you.
Although this is possible to do with the Fuel Rod shot, it is not safe because the plasma is controlled by gravity. It may sometimes hit the tree and damage the player.
