I like the fact that you can sprint.

Also:
Animation features a smilar level of advancement. For the first time, Bungie has implemented motion capture. A majority of cinematic sequences are based on captured actions. Onscreen characters exhibit an animation technique called variable gait blending. Simply put, it means that as a character changes speed, the animation of walking blends seamlessly into running, which likewise, blends into sprinting. When turning on a pivot, players no longer appear to stand still and simply turn in a circle. In Halo Reach, they move realistically as they pivot, lifting their feet and moving their bodies in reaction. For facial work, Bungie enlisted the aid of Image Metrics, a company some gamers may recall....With their aid, human faces now appear dramatically more lifelike than in previous Halo games.