i just figured out that my previous glitch works on army base too! and maybe the earlier levels, for the army base its all the way at the top and walk against the left wall, hold space, float, but this time if you keep holding space you can float AND move left or right in the air :P
police HQ HUGE glitch. go up one level and go allll the way to the right, keep walking against the wall and hold space, you will float in the air so the zombies cant attack you and pile up right benieth you. let the group build up and fire away for fast and easy money, no mercs or barricades needed :]