HALO is one FPS that really did introduce many new gameplay elements. It offers all that is said below and the modifications already in development look to refine and improve the "HALO experience" even more!
Adds brutal AIs to bloodgulch that all fly banshees that can explode!(like the banshees in single-player). This mod also has its own Installation/Uninstallation program! NOTE: this is for the original Halo: Combat Evolved NOT Custom edition. Back up before you install.