You know in the new Berlin map, there's a ladder where you can climb to the top of the tree on a little wodden 'floor'. It's really an excellent place to kill off germans without 'getting detected' although there is one problem with it. The wooden 'floor' is too small! It's really frustrating when you climb up a ladder and suddenly fall down to your death because the damn wood floor is too smal! :( Stupid tree ladder!
... this has never happened to me. just crouch when u get to the top, and dont go running off.
Theres also one on makim I belive. (theyr very well hidden, im not sure what maps they all on)