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!
Map Mod for Halo: Trial Mac. Turns warthogs into Go-Karts and make walls climbable. Simply place existing Blood Gulch file with the one included. Make sure to back up original file. NOTE this is for the Mac version of Halo: Trial.