Don't know if this is well known or not, but you can't be detected on the radar while crouching in crucible. Hard Light penetrates through Ward of Dawn slightly. Your Ghost can open doors that don't normally open. (Try pressing select while next to a door that can be opened while only in a mission.) You can boost your sparrow by quickly releasing and pressing the boost button. (Don't let the rockets go out.) You can sprint a bit to shorten the reload process for mini guns. (Only works as soon as the number changes.) Speaker emblems increase your chances in being invited to raid parties because the emblems are slightly brighter, attracting the human eye.