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!
Two teams of Marines wage war in Sunny Sharma's BG-Sorrow. Meant to be played with all vehicles enabled, as the AI will drive all of them properly! Both teams also get a banshee and a falcon, which will respawn every minute or so. Enjoy!