Our strategy for Lockdown is dodgy at best. We basically do that room in the 2nd floor of the corner building, with one person in the doorway shooting down the hall and the other person in the room shooting at the stairs.
While technically not a hack or glitch it is taking advantage of the game mechanics (ie, taking advantage of the fact that enemies and players can not walk through each other).
I think a lot of people have used this trick before but while it looks easy it's actually quite tricky, especially at higher waves.
We'll leave it up to you to decide whether this is a proper legit strategy or not. (Personally we're not sure and we probably shouldn't include it when we list our leaderboard rankings).
