The online Crossfire map has a very good sniping location. The spot can only 
be reached when you are playing the old school free 4 all section. The 
building at the very end of the map on the opposite side of the bus. You can 
get to the very top of the building that is around the corner. First, get to 
the second story where the chair is found. Get on the top of the chair 
facing the wall and jump. You may have to run and jump, but eventually you 
will catch an edge. You can then work your way up to the perfect sniping 
position.