Halo 3. No doubt many of you reading this post have played it. I'm quite willing to bet many of you enjoy playing it every evening. Whether you play at a social of professional level, this is a tip that can really up your game and help you rack up the kills.
In Halo 3, the battle rifle acts a little differently from in Halo 2. In Halo 2, the battle rifle projecticles would travel relatively straight and wouldn't spread too much over long distances; however in Halo 3, this isn't the case. Over medium to long distance the battle rifle has a bit of a weird spread which will cause, when aimed at the head, some bullets to miss their intended target and impact on whatever solid surface it next encounters.
This issue is caused by recoil on the rifle which causes some bullets to be fired ABOVE the enemies head. To counter this, aim at the subjects chest. This will increase the ratio of hits to misses on the battle rifle as the recoil on the weapon will cause the bullets fired at the top of the "rise" during firing to be fired at the head. This little trick means instead of firing 5 bursts at your opposition to bring him or her down, you only need fling 4 bursts their way.
To see this method in action, take a peek at this video by Major League Gaming (MLG)