The term is usually used in the popular shooter game "Halo 3 ." "Xbox Live Warriors" are people who don't die when they're no-shields. Xbox Live warriors are usually people with amazing connections and their bullets always registers in every game. Although other people shoot them, their bullets never registers and the "warriors" end up killing them.
Person1: Wow dude that guy is one-shot my X!
Person2: What! I put 5 shots onto him and he just won't die!
People such as Tensor and Snip3down are Xbox Live Warriors.